Before I elaborate on the question let me first tell you my situation.
I've started to DM a D&D 5e game last weekend, and thats my first D&D 5e game ever. So I kinda lack the intuitive gut feeling for balancing I have in games I'm more familiar with.
The 4 Players have formed a group with an average AC of 17.75, A paladin (med armor+shield) a cleric (likewise), a barbarian (shield and 18 con) and a monk(19 dex and 18 wis). We got these stats by doing 4d6 drop lowest stat rolls.
I call it the Panzer Batallion.
After taking only 2 damage from a medium and 4 from a hard encounter I chucked something about 30% over the "deadly" treshold at them. The Paladin and the Cleric had to pick someone unconscious up, but they made it without having more than one unconscious party member at a time. And the cleric still had a spell slot left.
I was pretty surprised, as far as I know that is pretty unusual.
Even more so because they were level one – which doesn't leave a lot of room for error.
Now the problem I need to solve:
Next weekend the rogue will join the action, and I'm fairly certain he will have a lot less AC.
I fear that everything that will challenge the tanks will kill the rogue outright.
And anything that would be appropriate for the rogues level of staying power would bore everyone because the tanks would just slug through it and be done with it, so the rogue doesn't really get to do something either.
As of now I have only one idea to deal with this:
Pinning the tanks down with weak but numerous enemies while some ranged foes pose the real threat. The rogue could sneak around the melee and backstab the ranged guys to get his spotlight and save the day.
Unfortunately that would get old pretty fast…
What else can I do to make combat engaging for everyone?
Any advice is appreciated, even more so if you can crunch some numbers why it would work.
Best Answer
Overall, I don't think you need to do anything differently.
5e's bounded accuracy tends to ensure that all things are hittable regardless of level. At level 1, those sorts of ACs are high, but it's not that big of a deal and not unhittable (just unlikely). You'll find those tanky players will be hit more regularly by the time they reach level 5 and enter the next tier provided you aren't handing out shields and armor with high pluses on a regular basis. Those players will be able to endure because attackers need to roll better than a 12 to hit them (but that'll still be pretty regular) and they'll also have a larger hit point pool.
As for your rogue, this player will do as a rogue does and interject themselves to make high damage attacks then slink back behind their heavy hitters. At level 2, this will happen all the time as the rogue gets arguably their most useful ability, Cunning Action, which allows them to hit and run with ease in combat. Furthermore, it should be noted that a rogue doesn't need to melee an enemy in order to easily sneak attack them. All they need is an ally with 5' of the enemy (and not be disadvantaged) to attempt a sneak attack, so ranged sneak attacks are almost always on the table.
The reason your Deadly encounter didn't go too badly was because of the game's bounded accuracy and preference for multiple encounters in a row as opposed to just 1 or 2 fights a day. You do have to be careful about spiking the CR, though. An enemy with a +6 attack bonus or better combined with multiattack, can pose a real threat of punching through that armor very quickly. Combined with the limited hit point pool at level 1 means that almost any hit can be devastating quickly. Personally, I often recommend getting your players to levels 2 and 3 quickly as that's when they get a lot of their features that promote their survival as well as gives them a hit point buffer for you to rely on in case of enemy's lucky crit.