Current classes/jobs are too simple

[kyuven]

Do you know how SE can improve difficulty of this game? Make boss AI better, put the damn RNG they have in this game to good use and stick it on Boss and mob attack patterns. That would increase difficulty.

Losses due to not knowing mechanics are annoying, but acceptable.
Losses due to RNG are infuriating.
There are already bosses that have RNG in their attack patterns. Such as t10's final phase. Or Savage t8.
The problem is you need to balance RNG usage with actual skill. If you use RNG for boss mechanics, there will end up being victories due to luck, not actual skill. Employing patterns means that the victories are legitimate. Thus, the RNG is never used more than between a set of mechanics tested to actually be doable. For example, target selection for t10's prey, Scylla's tethers, most of t9's mechanics, etc.