Marksmen in oblivion was OP with poison. Well that and any weapon with poison in it, and it happened because I think poison ignored the difficulty level...
My way to “fix” it would be this…
1. Give a big’ol damage bonus to any character that successfully completes any attack while in sneak, but give an even bigger’ol bonus to marksmen attacks. So someone has a real incentive to choose that has their primary play style.
2. Give sneak/marksmen penalties to players wearing heavy armor. So yeah, my lightly armored sniper can do a lot of damage in sneak, but if he blows his cover, he could be in a lot of trouble.
I mean they already did most of that stuff, just not enough. My heavy armored axe swingin warrior type could get the same marksmen sneak bonus as my lightly armored assassin, so why bother?
+2. But of course marksmen can't kill with 1 or 2 blows, even the first being a sneak attack. I think they should be more worried about not putting OP stuff like oblivion poisons (not with the damage they did), levitate in morrowind, very strong enchantments that are easily recharged with azura's star, etc...