I think the level-sync feature may be a bit over-generous in the stats it leaves level-synced players with, at least for the really low levels. It might say you're level-synced to level 10 or 12 or whatever, but you'd still be doing more damage than an actual level 10 or 12 player likely would.

I'll generally try to avoid zerging through all the mobs if someone else is there, but if there are a bunch of other people there, that doesn't always work. (Even if we take only a few of the mobs each, it can turn competitive. Consider for instance, if 6 or more players are each trying to claim around a fifth of the mobs. There just aren't that many fifths.) Boss-type FATEs are usually a bit easier to ensure that everyone gets a chance, as nobody will be one-shotting those.