No, really, you are always weaker by taking blighter, because you lose ALL your druid class features. Without any funky RAI abuse, the Blighter has 5 dead levels from the first time you ever see it, and at level 15 it gets 9th level spells from a crappy list, and even if you do a dual progression, you've still got 5 dead levels, and probably a really crap low caster level. A 15th level druid and a 15th level blighter could square off and the druid would win every time because the druid has 8th level spells and 3 paths to power, while the blighter has only 1 because he can't keep up with the druid's paths to power, as he only has 1 (he's got no AC, and he's 5 levels behind the wildshape arms race). The druid uses holly berry bombs from the air and laughs.
Also, no dice on AH because you lose your Animal Companion.
For giggles, let's compare a druid 20 to a theoretical Druid5/Blighter2/Bard4/Sublime Chord2/Mystic Theurge 8 and pretend that it works for both ninth level arcane spells and ninth level divine spells. The proposed theoretical build is still sorely MAD, while the druid has incredible saves and AC due to his +5 wild dragonhide fullplate, high con and wis, monk's belt + wildling clasp, and any number of ridiculous buffs and stuff. Also, he has freedom of movement, extended bite of the Foo, greenbound summons out the butt, an animal companion rocking nature's avatar, which shares his buffs... there is no way that a blighter who qualifies for the class normally will be more powerful than a druid.
