I think most of us can agree that restoration loop and the use of falmer helmet are glitches. But what about necromage's 25% boost from being a vampire?

The way I see it, there's really no other way to bring numbers back from legendary difficulty to master level. At legendary, it is 25% while master is at 50%. In other words, we need to be able to double damage output to be able to offset the decrease in damage. An example: before legendary difficulty, what used to be 500+ points of damage from a deadric sword is doing only 250+ (master difficulty halves damage), but only 125+ on legendary. To be able to kill the same monsters in the same number of hits, you need to fortify skills and smithing damage up to 1000+ to be doing 250+ of damage on legendary.

Now there are arguments against this line of thought naturally.

- legendary is meant to be difficult. Trying to game the system this way defeats the purpose of a higher difficulty mode once it becomes a pure numbers game.

- there are gear and shouts in Dragonborn DLC to increase enchanting effects slightly. Use those as legitimate ways to increase damage even if the increases are marginal when stacked.

Thoughts on the issue?

well, depends, from just looking at a rule lawyer's perspective, there is nothing saying that it would NOT effect being a vampire, and thus fits within the confines of the game, and thus is not cheating. On the other hand, the SPIRIT of the perk was probably that is was an anti-undead ability, and thus is not really meant to boost the abilities of being a vampire.

It's a single player game so anyway you feel like playing is fine. The "game" won't get mad because you are crunching numbers with stats.