D&D 5E Drawbacks to Increasing Monster AC Across the Board?

[Andvari]

I like lower to hit and fewer HP as it makes combat faster and feel more dangerous due to less time spend updating HPs and more risk from a “lucky” streak.

Unfortunately I wouldn’t want to mess with it in an existing system like 5E as it affects other things. Damage spells that bypass AC become more potent, for example.

 

[Tonguez]

I think its more fun to give monsters things like evasion and repositioning abilities or use cover and hide and terrain advantages, make combats dynamic - use lair actions for everything

 

[Uni-the-Unicorn!]

So, our group recently got to play several sessions of D&D 5E over the past few weekends. More than we've gotten to play consistently in quite some time, so that is good. Lots of fun.

However, one of the players has noted that it's very easy to hit the monsters. It seems a lot easier than previous editions, especially easier than AD&D.

By my calculations, between the minimum +2 proficiency bonus every character gets along with usually at least a +2 ability score bonus on the attack roll along with some other things, it seems like it's probably 20% to 30% more easy to hit an average AC than it was in 1E at low level.

Now, don't get me wrong. I really like 5E and am definitely not wanting to start any sort of edition war. However, I'm wondering if it might hurt to increase the monsters' armor classes by a few points in general and how far I could go in that regard without the ACs ending up too high when our group gets some characters to high level? Would a four point bump in monster AC be too much? I'm pretty sure two points would help, but not sure about going the full 4 points (or even 5 or 6) as it would likely break bounded accuracy and make high level monsters too invulnerable to lower level groups.

Has anyone done this? What were the results?

5e was designed to have a 65% bit rate which is indeed higher than many earlier editions. And a complicating factor is that rate is accurate only if you don’t give the PCs magic weapons. So, if you give the PCs magic weapons, and you want to have the same hit rate, then you do need to increase th monster AC to match.

 

[pnewman]

If you only raise monster AC's, but not monster Save DC's (which are also pretty low) you will benefit fighter type monsters more than caster type monsters. Unless that is an intentional choice, you may want to think about raising their save DC's too.

I just started a 2025 only Greyhawk campaign, and I am giving all the monsters +1 to ht and +1 to their Save DC's but leaving their AC's as is. I want the fights to be a little more hazardous, but I do not want them to be even more slow and grindy, and I think that raising monster AC's would do that.

 

[ezo]

Back to this stuff again...

I am in the rare camp of lowering monster HP and increasing AC. As it is, in 5E you might as well get rid of the attack roll and just roll damage. While the 65% rate concept is nice, it should be the peak, not the base. Because as it is, the peak is closer to 85-90% IME. At that point, "hitting" is boring and missing becomes the fun part IMO.

I don't want the slog to continue, which increasing AC would do, but by lowering monster HP that counters that issue. While 35% is certainly too low for some people, I think a base around 45-50, with a peak around 65% is best personally.