isoChron said:
7 (!) characters level 15 (clr, wiz, wiz/rog, rog, pal/ftr/rgr, rog/asn, drd)
So, let's see. We'll assume front-loaded Ranger(2) at most, Fighter(4) for weapon spec, that's still Paladin(11). 2 less HD, so 2d8+6 less hitpoints - TWO maximised fireballs against a Light Warhorse paladin's mount
might kill it, if it failed
both saves. Odds are it's HURT, yes, but definitely not dead.
15th level cleric, and an invisible spellcasting enemy - sounds like a good time for an Antimagic Field spell to ME. Pop a Widen on it, and crowd everyone together inside ...
15th level Wizard; if he's lacking a Permanent
true seeing, he's truly
earned the world of hurt coming his way. Just because of how well True Seeing preserves his abilities to target enemies when he IS in combat, it's worth the XP - or the GP for a magic item of one sort or another. With that, and a glitterdust, eh can "light up" the enemy spellcaster but GOOD.
Wiz/Rogue, I don't know what the level split was, but however the levels are put together, there're several options that each combination could take. Regardless, at least has Evasion, MIGHT even have improved evasion.
Pure rogue ... improved evasion. 'nuff said.
Rogue/Assassin ... ditto.
Druid, wildshape to something that flies, head towards the general direction the spellcasting noise came from. Should have the Blindsight feat, if he's worth the name "druid".
So, even accounting for the multiclassing ... I fail to see how a single, unsupported wizard
four leels below your party's level could possibly have been defeated, unless (a) your PCs were poorly built and/or played, (b) the dice were so strongly against you that a mob of blind kobold children (SANS buckets of snails) could have whupped yer backsides with one arm (and both legs) tied behind their backs ... or (c) the GM outright cheated.
I prefer (d), "this scenario never actually occurred". Unfortunately for your credibility, others seem to agree with that assessment.