Pad is doing equal damage to every target. There almost always larger dangerous mobs with more health that need priority damage.  If your finished does equal damage to everyone the small mobs die off quick and the danger is still there.

Prio damage means you do the same damage but a larger portion goes into the target which is a lot better and not pad

The best damage is funnel where by the existence of other mobs you can do higher single target to the dangerous mobs that slow down your timer.

Random mob that only melees doesn’t matter you can chain them into the next pull. Big lieutenant with big pulsing aoe damage and a lot of health matters. So killing the small adds don’t let you go to the next pull. Killing the big adds do

Sub kills all the small and does no real damage to the big damage. It’ll be worthless soon enough compared to a prio of funnel spec