Yeah, besides, haven't the actual Batman and Justice League books said that Batman's been around for 20 years and the League for 15? If so, Damian's age works out fine. The big continuity issue right now is that Young Justice's timeline is incompatible with Jon Kent's. Given that Jon was born after the wedding, which was after Death of Superman, more than 10 years should've passed since Conner's debut which was during Death of Superman, which would mean that Tim should also be ten years older than he was in the 90s. Dataweaver's right, Jon needs his original origin back.
I'd ignore what JSA is saying - it's probably an alternate timeline that's about to be negated by Per Degaton - thus stranding the time travelling Huntress in the present day.