Would evasion help low CR monsters against a high level party?

[Krachek]

Orc and other CR 1/2 are the rare monster a fireball can kill one shot.
And even using a level 3 slot, you need to roll over average!

Once you get CR 1,2,3 these monster have 25-50 hit points.
So you need fireball dealing 50-100 points of damage to be sure of a 100% wipe out.

The rules are fine as they are.

 

[Yavathol]

I remember a scene in SKT; the PCs were 6th or 7th level and approaching the Oracle. There is a long access corridor, at the end of which is a group of Uthgardt trying to open the door. My PCs stroll up, see the light from the Uthgart torches, and the wood elf makes a typically high perception check to identify them.

The Uthgardt spot the PCs and start to charge them, then the sorceror fireballs them (think she used the re-roll 1's sorcery point option). I'm pretty sure I did not screw up any math, but the whole group was annihilated, even the white dragon wyrmling! Maybe the leader survived, and then the fighter killed him with a long bow attack.

In hind-sight it didn't even seem worth rolling initiative:-( None of the enemy got close enough to even throw a javelin..Maybe this is an oddity with SKT since the giant size encounters are so long-ranged?

 

[Tony Vargas]

Some great suggestions there, thanks guys!

At the moment this isn't a problem, but I thought one of the design aims for 5e was to make it so that low CR monsters could still be used at higher levels; maybe that was dropped at some point during development.

It was, it wasn't and it still is. It's a major point of BA. And, it was a goal expressed in the playtest for very high level fighters & wizards to both be able to 'take on armies,' just in different ways.

And, yes, large high-damage AE's with half damage even on a successful save undercut all that.

"Different ways" probably wasn't meant to be "the wizard annihilates whole formations with a few of his lower-level spells, while arrows rattle of his protective force-field" while "the fighter charges into the ranks, wreaking carnage for almost a whole minute before being beaten down or pincushioned."

Or, rather, that's exactly what it was meant to be, it's just not what all of us may have wanted.

I think I'll try the 3e style Evasion as several people suggested. I don't particularly like giving Orcs and Uthgardt special rules and equipment like large shields and tarps; they're not expecting to be attacked by a wizard.

And sauce for the goose.. Seems less unfair if the PCs have that option as well?

It could be a fine option for PCs. If a PC gets caught in a save:1/2 area that would insta-kill him even on a successful save, make it save:neg. Instant death on failed save, live another round on a success.

They'll most likely still all die if facing something like that, but a few of them might get some licks in, or delay the enemy for more than one round.

Thinking about it overnight, spells like sleep still take monsters out of the fight instantly, there's probably others I haven't thought of..

Sure, but sleep needs to chew through all the hps present, so sheer numbers still matter.