Yeah, I can see your point.
Wouldn't a solution to that be adding a buffer class/job. Like some mobs cast stuff like "Enfire" etc to add a fire property to their attack. I assume they can create a job/class that does the same for party members. Wouldn't that sort of solve the problem for monks and other DPS classes that aren't BLM?
I guess that'd make that class mandatory though, hmm...

I dunno, I just think it'd be cool if the game included elemental properties and I do think it's possible if they balance it properly :P (then again, I'm still new to this game, so I prolly don't know much >.<)