Yeah, I've had little problem taking gyms by just doing repeated attacks - you just have to get the prestige down to zero, so 1 or 2 weaker people with enough revives can pretty much clean house. Holding the gyms is the hard part I think.
Of course gym battles are a lot more simple and fixing the many issues both combat-wise and in general take priority compared to adding such mechanics in.
It's not an issue, LTE is fast enough. For multiplayer we take into account every bullet and sync dozens of players in real time.