2 first strikes and march is barely different? No way. Imagine if that came on a unit that had utility before the last 10-20% of the game, it'd be one of the best UUs ever.
Sorry to keep doing this to you TMIT but that is 1-2 first strikes - not 2 first strikes. Can be described more like 1.5 if you must.
To the OP, IMO no adjustments should be made to UBs or UUs without consideration of the leaders who use them, and the starting techs for the civs.
I've always figured there will always be more powerful UBs and UUs in isolation, just as there are more powerful traits in isolation, but that usually when one of them is weaker, the other will be stronger, thus overall balancing out the leader.
Obviously when you fiddle with Unrestricted Leaders all balance can be thrown out the window, but I think that was only put there for fun, not because the UBs and UUs were "balanced" in any way.