At lower levels blm in dungeons can be useful as crowd control with sleep and that really shouldn't be overlooked. Once you get fire 3 and blizzard 3 the job and your rotation change up a bit. I find blm to be a challenging and rewarding job at end game. And while it's true the basic rotation may be simpler than other DPS jobs there is a lot of nuance and skill needed to maximize your DPS uptime casting spells in most of the end game fights.