Notmousse said:
Or maybe it shouldn't be against a single monster with SR and practically nill (2 for a GWRD) touch AC?
You're right- the single huge dragon encounter is biased against the evocations, and towards the orbs.
Ok, let's stack the deck against the Orbs instead. (I'll try and show all my math.)
We'll pick an appropriate CR for 15th level PCs- CR 16 would be a big, but not huge encounter.
Now we'll choose the CR 16 monster from the MM with the _highest_ touch AC. It's the Cornugon Devil with touch AC of 16. It also has SR 28, Fortitude and Reflex saves of +16, and Cold Resistance 10.
We'll give both PCs 16 Dex (including a +2 item) and a 22 Int (25 pt buy: starting 15, 3 boosts; +4 item).
Since this isn't a huge encounter, the casters don't use their 8th level spells. They both toss a 7th level spell, Maximized versions of Orb of Cold or Cone of Cold.
Connie does:
Ranged attack bonus of +10 (+7 BAB +3 Dex) means she hits on a 6 or higher or 75% of the time.
Average damage: 15*6 = 90(*0.75)= 67.5
-10 for cold resitance
=
57.5 hp. (11.25% of the time, the devil will be blinded.)
Evan does:
Caster level of +17 (we'll even give Evan Spell Penetration to help him) means he succeeds vs. SR on an 11 or higher, or 50% of the time. Reflex DC is 20 (lvl 4 spell +6 Int). The devil succeeds on a 4 or higher, or 85% of the time.
Average damage: 15*6 = 90(*0.50)= 45(*0.15+0.5*0.85)= 25.875
-10 for cold resitance
=
15.875 hp.
But Evocations are used against multiple opponents! let's cluster 4 Cornugons within the Area of Effect:
15.875*4 for AofE on all the devils =
63.5 hp!
That's only 6hp more than Connie (+10.4%). And she has an 11% chance to blind.
In other words, even when we stack the deck for the Evocation user [High touch AC, Spell Penetration feat vs. no specific feat for Connie, 4 opponents] it comes out pretty even.
Almost any other encounter than this one will get worse for the Evocation spell up to the high CR dragon encounters Rystil has brought forth.
That's why the orbs seem broken to me.