Heavy Thrust is personal damage increase which is nothing up scoff at, as no matter whether the damage appears worthless or not it's still something you have compete control over, rather than relying on others to boost your damage. Also there are several other jobs with their own damage buffs as well that form part of their rotation, Hotshot (MCH) Jinpu (SAM) Greased Lightning (MNK), I mean the list kinda goes on so it's not just a DRG thing.

I mean in the end if you choose to use certain part of your toolkit is completely up to you, but you'll find it much more useful to take advantage of everything at you disposal. Not to mention in raid environments, not playing optimally can often attract scorn from others hoping to get high output from all party members.