I don't think it would be reasonable. 200 guards in particular fighting at once would easily overwhelm 4 level 7 characters. They are going to overwhelm them on action economy. 4-7th level characters have 4 reactions a round, meaning there is nothing stopping most of them from moving in and out of combat.So with all the talk of game balance of late, something that keeps coming back up is the notion that players that get to rest more often and fight less encounters in a day will find challenges easier than a party that gets the full 6-8 encounters.
So the real question is: Well how much more can a party take on?
So we could start with a simple premise: What if the DM just pushes the entire daily adventuring budget into a single encounter. Aka its expected the party will go hog wild, throw every bit of juice....and be completely spent by the end. So what would that look like in terms of challenge?
So lets take 4 level 7 characters. They have a daily adventuring budget of 20,000. So here are some example challenges that would fit their entire budget. I had to go a bit under or over much of the time, as often adding just one more of almost any monster just shoots the encounter XP way up.
So just taking a look, what do people think? Do you generally feel like these would be really challenging encounters for such a party who is going "all out"? Would this crush them into the dirt, would you expect them to win with no problems?
- A Demilich (CR 18)
- Two Young Red Dragons (CR 10) - 17.7k
- 3 Githyanki Knights (CR 8) - 23k
- 4 Mind Flayers (CR 7) - 23k
- 5 Flesh Golems (CR 5)
- 8 Black Puddings (CR 4) - 22k
- 200 NPC Guards (CR 1/8)
If this produces reasonable results it might be the way to go for people who just want to do 1 "big combat" a day, and help them understand what you really need to throw out to challenge such a party.
2 dragons and a demilich likely would beat 4 7-th level characters as well. The adventuring budget is based on short rests and recharging.