The only pull size is the one you are comfy
No. Just no. The only way to become better is by pushing your limits. You don't become a better runner by jogging from the chair to the kitchen. You don't become better tank by pulling one pack at a time how you're used to in that first Sastasha's run. Try doing slightly more every time, analyze why you have failed if you did and how to do it better next time. "Do only comfy pulls" is a way to waste party time. If you don't want to work hard, don't register for duty. We have enough bad players everywhere already.

if you have 2x Dragoons then no, your wasting more time dealing with large pulls
It's heavily depends on a level. In low dungeons, where lots of jobs won't have good AoE, that is true. In 50+, however, any combination of jobs have enough AoE abilities to make big pull worth it. Assuming DPS players and healer actually use those abilities, ofc.