How to beat Grand Widow Faerlina on heroic

He's mostly a situational card.

As you mentioned you can silence him, Most notably for me I typically use it in my priest deck (as priests have mass dispel and a 0 cost silence) to troll and get a monster on the field. Since it does not attack and doesn't have taunt 90% of the time players let me keep it on the field. Then the next turn I Silence, Divine Spirit, Inner Fire, and boom they've lost 10HP or more if I use multiple Divines or Power word: Shield.

Additionally, I like having Defender of Argus in my decks so I don't have to run as many taunt cards and he's not a bad addition, as sometimes when your enemy has board control you can place it down without the enemy killing it as they don't see it as a threat. If they do kill it then you've re-directed 5 Damage that could have went towards you.

I use it as an underdog-card in most situations. It has it's uses but by no means is an amazing card. I mostly keep it around for the laughs, as I play to troll not play to win :D

Uses:

• Rush: If you get him early with a (0) cost silence in a priest deck it can catch your enemy off-guard
• Board-Control: If you're losing it can be difficult to gain board control back. This card is commonly left alone as it has no immediate threat. Even if it is killed before you can silence or give it taunt it is a cheap card so it is at little loss to you (other than maybe card advantage)
• Buff: Typical usage of Silence or Taunt.
• Full-Field: This one is a long-shot, but you can use it as simply another card on the field. Some cards such as Frostwolf Warlord could benefit from having another minion on the field. Hell, you could throw him in before a Brawl just to have a slightly higher chance at killing all of your enemy's minions.
• Silence Counter: If you give it taunt it can act as a deterent for your enemy to silence away your taunt since he'll then be able to attack (As mentioned by "z -" below).

A friend of mine has had luck with a Freeze-heavy mage.

Between cones of cold, water elemental, and frost nova, you should be able to protect yourself while establishing board presence. Don't forget to add two Flamestrikes to your deck -- they'll wipe all of Anub's 4/4 Nerubians at once, which is great for in the late game when he's managed to keep 2 or 3 on the board.

Your goal is to survive long enough to drop big minions and waste him. Alexstrasza (if you have her) will deal a quick up-to 30 damage for you, while big minions like Boulderfist Ogres can take hits from the 4/4 Nerubians, and wail on Anub if left unattended. I was able to field Gruul as well.

Beyond that, keep some beefy taunt minions with at least 5 health (Sen'jin and Sunwalker are good choices) to soak up and outpace his minion growth.

Finally, Anub will only use his hero power if he can't play cards -- with a little luck, you will have fewer 4/4s to deal with, and eventually be able to push through.

Good luck!