Okay, so I was looking into Spellfire Channeler some more, trying to find some use of it (since it really does suck). Unfortunately, it cannot voluntarily expend its entire Spellfire pool (up to Constitution (score, not modifier) x 5 eventually), so that removed one more thing that the class could have potentially redeemed itself with to some small degree. I did find one... not even good, but at least decent for what it does... use of the class.
As a 2-level dip, it increases the healing potency of Spellfire rather significantly. It increases from 2 per level to 1d4+1 per Spellfire level (average 3.5, a 75% increase). Since you can store up to your Constitution score in Spellfire levels, you can be a fairly efficient heal-bot if you have a constant source of spells: as mentioned before, the Warlock is the best fit. Since you only need 2 levels, either be a Warlock 18/Spellfire Channeler 2 (not necessarily in that order), or pick up a Cohort. This means you can heal all day long (or do it the other way around and make your cohort heal you all day). A single level 9 Eldritch Blast gives you 9d4+9 hit points (31.5), making out-of-combat healing completely free all day long. And in-combat, the Warlock side comes into play, letting the character do all the other things that warlocks ordinarily do. Is it great? No. But at least it's something even remotely salvageable from this prestige class.
