BLM is one of the most stable jobs in the game. Your specific criticisms reveal a misunderstanding of the jobs fundamental gameplay loop, I'd highly recommend reading some guides.

As someone who's mained it since Creator and generally considers myself decent at the job, my only real criticisms of it are:

1. Inconsistent nature of Mana-tick timings, leading to inconsistent fight timings for potential b4 skips
2. High spell-speed builds outpacing Polyglot generation, sometimes forcing you to be even more immobile on the back of the already fairly rigid b4 skip opener.