It's a very Blizzardy Thing to do
I think it's bad for the game thematically -according to lore, the Draenei worship some advanced interstellar species and specialize in light magic. They shouldn't be into shammanistic religions, since that's the religious background of their enemies the orc.
Meanwhile, blood elves worship Sun magic, which, unless you're thinking in a weirdly simplistic way, means they shouldn't be worshippers of Light either. Instead, it's almost as if the defining characteristic for what religious orientation they can be is their posture!! (slumped over as the draeneii, orc, tauren and trolls, or standing erect, like the humans, dwarves and blood elves)
However, in all of their games, Blizzard has always chosen fun and playability over more idealistic concerns. WoW is a great example of a game that's designed less as a virtual world experience and more as a fun playground. Too bad they took the shortcut to giving us new toys instead of designing new classes.

L