With Season 3 here, lots of new items have been release. One in particular is the Sightstone, and if you didnt know this item allows you to basically have unlimited wards and a decent amount of health with an upfront purchase. My previous reasoning for GP10 was to make up for the lose of gold from purchasing tons of wards and having no serious income besides assists and the occasional minion/champion kill. Season 3 also upgraded the amount of gold you get over time, combine that with 3 quint GP10 ruins and masteries in GP10 your making a decent amount of gold.
So, would it be viable to change my build completely away from GP10 and rely on assists? I use Leona, Taric, Blitzcrank, or Alistar when I support (i have others but they are the best in my opinion). Although I havent gone back to Ranked since I started to mainly support, lots of assists are pretty easy to come by. My current build focuses half and half. Runes/Masteries have a focus around GP10 and survivability, while my item build focuses on damage and survivability.
Janna excels in supporting teams.
Howling Gale which launches enemies into the air in a line.
Eye of the Storm shields an ally for a determined amount of damage and gives a damage buff, and it is the only shield capable of protecting turrets.
Moonsoon is a teamfight changer ability as it aoe heals your team and blows away enemies in Janna's ability ratio
Tailwind grants 3% move speed buff! 
Karma can contribute with great magic damage bursts. Additionally, she has a single target movement speed buff. Karma is a special support champ in the sense that she does not posses an ultimate ability per se, but her ult, Mantra, gives her a bonus effect on all of her other 3 spells:
Heavenly Wave + 
Mantra = AOE Heal in a cone in front of Karma
Spirit Bond + 
Soul Shield + 
Kayle makes an ally invulnerable to all damage for 2-3 seconds! Additionally, she heals allies and slows enemies, making her a very nice support pick. Unlike Janna and Karma which build defensive and AP items, Kayle builds Hybrid items like Hextech Gunblade and Guinsoo RageBlade. 
Divine Blessing heals up an ally and grants a movement speed bonus.
Intervention grants invulnerability for 2-3 seconds, which can completely alter the course of a team battle if used well. 
Lux is considered a support/mage. She can tear up teams with her chain of abilities, possesses a 2 unit root, AoE slow, and an amazing Ultimate.
Prismatic Barrier shields an ally for damage. 
Morgana is just like Lux in that she is a support/mage. However, she is considered a better support for the shield she grants:
Black Shield is a very unique shield that blocks magic damage and any negative effects: all snares, silences, blinds, etc. This shield scales with 80% of her total ability power. It is a total carry protector and game changer skill.
Sona is the queen of support in my opinion, closely followed by Soraka. All her abilities except for the ultimate give your teammates a buff and she can not be ignored damage wise. 
Hymn of Valor is an aura granting a buff to damage and ability power. 
Aria of Perseverance is an aura that increases armor and magic resist to allies. On cast, it will heal the most wounded ally nearby. The Powerchord bonus decreases total damage output of the target by 20%
Song of Celerity gives a temporary movement speed buff to your allies, in addition to the aura which grants a fixed movement speed bonus! 
Soraka is one of the oldest support champions, and one of the most powerful ones. She has a single target heal plus armor buff and the ability to grant mana to an ally.
Astral Bleesing heals for a decent amount while granting 20-80.
Infuse grants mana to an ally. No other hero can boast an ability like this.
Wish is a global heal. The epitome of an incredible support heal.
Consecration, her passive, increases magic resistance for nearby allies by 16.
Taric can heal and has an Armor Aura, Damage Aura, and a Stun, which makes him a reliable support character. However, one of his downsides is being a melee character unlike many of the others mentioned.
Imbue, if casted on an ally, heals Taric and your ally. If casted on Taric, he heals himself an additional 40%.
Shatter is an aura that increases allies' armor by 10-30 and increases Taric's by double this amount!
Radiance heals Taric by an amount per second while granting an aura that increases attack damage by 15-45 (and double that on Taric). Make sure to use while taking down towers and in team fights!
Zilean is an amazing support champ with the unique ability to revive champions.
Time Warp is a single target Speed Buff/Debuff
Chronoshift revives a fallen enemy with scaling (200% of AP) restored HP and Mana. That's like fighting a 5.5 vs 5 :)
Heightened Learning, his amazing passive, gives all allies an 8% bonus to experience gained!
Best Answer
You list primarily tanky supports, who were hit the hardest with the removal of Heart of Gold. This leaves two other GP/10 items: Philosopher's Stone and Kage's Lucky Pick. I ignored Avarice Blade as I don't feel it compliments the support role.
A Philo stone can build into Shurelya's Reverie, Eleisa's Miracle, or Ohmwrecker. Shurelya's is still a great support item, and Eleisa's reduces the cooldowns of the summoner spells Heal, Clarity, and Clairvoyance. It can also free an inventory spot if purchased early enough! Ohmwrecker is outshined by both items, and I don't recommend buying it on a support.
Kage's Lucky Pick turns into Shard of True Ice, Twin Shadows, Morellonomicon, or Will of the Ancients. The first two are most viable on a support, and the Shard continues to provide GP/10.
So a lot of things affect whether GP/10 is still viable.
For a Philo Stone:
For Kage's Lucky Pick:
Another new item is the Sightstone. For an investment of 950 gold, you can place up to 2 wards at a time, with each ward lasting 3 minutes. The Sightstone holds 4 wards total and refills when you return to base. This breaks down to 50 gold/minute, and starts saving money after 19 minutes (assuming you immediately place wards when available). It also provides +180 health, making it a strong choice for tanky supports.
Previously, GP/10 items were essential to compensate for the cost of wards. This is largely mitigated with the usage of a Sightstone, freeing money for other items.
A Philosopher's Stone costs 700 gold and pays for itself in 23.33 minutes. Kage's Lucky Pick costs 765 and pays for itself in 25.5 minutes. These times are halved if you sell the item. Because it takes so long to make money from GP/10 items, it's best to buy them as early as possible.
Compare this to the gold granted from kills/assists. A champion who hasn't been killed is worth 300 gold, and 50% of that for an assist. The more times a champion is killed, the less money the kill rewards, with a minimum of 15 gold.
Since 2 GP/10 items provide 60 gold/minute, you have to get a 150 gold assist every 2.5 minutes for assists to equal GP/10 items. You can get an additional 5 GP/10 from Quints and masteries, resulting in 90 gold/minute and needing an assist every 1.66 minutes.
The new pick-pocket mastery offers an additional avenue to generate gold. Unfortunately, this isn't very viable on melee supports.
While supports are no longer required to get GP/10 items to support expensive ward-buying habits, these GP/10 items are still cost-efficient for longer games AND they upgrade into items that are very useful for most supports.
Ultimately, the decision to buy GP/10 items comes down to play-style and preferences. If you prefer to play aggressively and need extra stats to stay alive, skip GP items. If you're trying to maximize gold gained, GP/10 is still the better choice (unless you can get an assist every 1.6 minutes!).
tl;dr: GP/10 is still very viable, especially since those items build into new support-focused items. However, it's no longer a necessity since the Sightstone makes warding much cheaper.