I posted this in another forum chat, and thought I'd bring it up to the greater community as a whole:
I think the whole of vampire is backwards.
A vampire in Elder Scrolls is supposed to be physically stronger when in lower stages but stronger in all other aspects when sated. Right now it's the opposite, so here's how I would change it:
1. the extra fire damage you take is 20% regardless of your stage, but you take an additional 10% when at stage 1. This shows that you are not sated, and thus are more vulnerable.
2. Health recovery is reversed. Stage 1 is -100% / -70% / -40% / and stage 4 is -20% (instead of 10%)
3. Reverse the regular ability cost increase as well. Stage 1 is +12% / +8% / +4% / and stage 4 is 0.
4. Vampire ability cost is a bit different. Starting from stage 1 it would be a cost of +8% / +0 / -10% / and at stage 4 it would be -20%. So at stage 1 your vamp abilities cost more, stage 2 they cost the base amount, then at stages 3 and 4 they get reduced in cost but never as much as the current version.
5. Finally, the last change I'd do for base vampire. Damage. Starting from stage 1, your overall damage is increased by this: 7% / 3% / 0 / 0. This is to show the ferocity of a hungry vampire, and is a great buff with an equally great downside.
Other changes would include stage 1 vampires are attacked on sight by guards, stage 2 vampires get the current thing of NPCs not trusting you and won't let you buy or sell. Stage 3 and 4 would be fine in towns aside from casting vampire abilities.
As for Blood Frenzy, I don't like it not having a cap for both damage and damage you take, it makes it a pain to use and incentivizes players to find cheesy ways to make it last longer. I'd change Blood Frenzy (where it increases cost by 20% every second but doesn't increase the damage you deal with the skill) back to 10% every second, but cap it at 200%, meaning it can't go above costing around 4k per second. I'd make Simmering Frenzy have the cost be 20% hp every second and cap it at 200% as well, but give it 10% increased damage every second up to 100% so people can't figure cheesy ways to game more damage out of it. And finally, the other morph I'd just make a skill. It no longer toggles, but costs a flat amount of 50% of your current hp (I'd also increase the amount it gives you by a little bit), and lasts a flat 12-20 seconds when it's level 4. Costing 50% of your current hp makes it synergise with your other vampire abilities in an interesting way.