Not sure your ideas are the solution, but snipe and to a lesser degree maim lvl 15 skills need a boost. More convinced of this than ever, now with the addition of DA.
Snipe is meant to deal dmg and finish an opponent, stopping regen does little to further this. I think a 5% crit 1.5x crit chance to autoattack and a 10% crit 1.5x chance on snipe seems more appropriate and gives a legit reason to choose this. Given that at lvl 15 you likely already have crit items or are against heavy hp stacking, it brings usefulness to late game snipe, something sorely lacking now.
An alternative to this could be adding a 500hp hemorrhage over 5 secs. This gives added dmg, but allows the opponent a chance to pot, presumably from behind cover.
Either of these would be reasonably large buffs to reg that may mitigate the need to nerf UB, LE, and DA.