They will not be taking out mob AoEs and markers. This is a staple part of combat and would require them to rework every mob in the game, including overworld trash mobs. The likely changes you will see are:
1) Streamlining of action combos
2) Rework of cross job skills (we already know know this is becoming role skills, just not the fine details)
3) Removal/reworking of underutilized skills (once more we know this is happening, just not the details)
4) Changes in damage calculations based on stats, potency and weapon damage, likely minor tweaks
5) Refinement of action animations including animation locks
Beyond those, I wouldn't expect much else.