I cannot comment on the Snipe changes because they're not my thing, but I did make the IO set, so that one's on me. An interesting point is that during the closed beta, PVPers were all about the fast snipe, but in the open beta here, PVPers are all about the slow snipe. Either different meta or different tastes, interesting either way.
The set started explicitly just for the "Fast Snipe" IO, with the other pieces having no interrupt reduction because they would be completely wasted if you slotted the Fast Snipe enhancement. This was actually the exact same complaint I got for Sudden Acceleration, where most of the enhancements add +Knockback just for the KB2KD to take it all away. Slotting it and not the proc will leave you with the power's default interrupt time, which is indeed terrible. But adding interrupt time would take enhancement values out of other aspects, which leaves to the problem that Sudden Acceleration has, where only the KB2KD proc is slotted because the other pieces are in direct conflict with it.
The range bonus is 5% specifically because it was requested to be anything other than 7.5% because "that's so easy to get already" . The rest of the PVP bonuses were honestly picked to fit the "pair" with the PVE one, health/regen, damage/accuracy, endurance/recovery with the last one going for Recharge as that's where most of the other PVP sets put it. They are not set in stone; this is a beta.
The accuracy bonus is 7% in every other PVP IO set, which were taken as a template. However since this particular set is getting a lower range tier, giving it a higher accuracy tier would be a fine tradeoff.
The health bonus is in line with Gladiator's Strike at 3 slots, but now I see Gladiator's Javelin has 1.88% also in the third slot, so that's an easy tweak.
The recharge bonus is on the sixth slot in nearly all of the PVP sets, the exceptions being Gladiator's Net and Panacea which aren't damage sets. But swapping it to the fifth slot would not be a big deal. Gladiator's Net also has 3% Recovery as a sixth slot bonus so that seems in-line.
Any particular reason why dominator snipes are being nerfed so severely? Why not leave their damage alone?