nothing is stopping you from a rigid style other than the sp cap. you can create specialized builds, but for some specialized builds, the best thing is a hard monster, for example gladiator to excel, needs tough monsters. its the highest single target damage reduction. for being a pure healer you need stuff that hits people hard. This stuff exists, but only on higher than 10 levels exp, which they give no reward for.
the same thing happened in ffxi, when the focus shifted from killing IT monsters to zerging lower VT infinitely, pld blm whm smn all went down in value. DPS and DPS buffers with one cure person took control as the party of the norm, blm were forced to create blm parties. The SP reward system is to blame for many peoples beefs, and the lack of certain types of content.
the SP change is the main culprit