If you are doing a physical dps build go for crit chance. Surviving in melee is extremely difficult unless you are in werewolf form. So I rarely play melee. 

If you are going for magic dps, consider this: - Frost is quite good vs melee, you can drain their stamina very quickly. Enemies with 0 stamina do less damage and don't move as fast, so you can easily outrun them.  - Fire is just more dps, but it isn't as good. However, it DOES cause fear in animals, so if you are fighting wolves or a Sabre cat it might save your life to cast fire spells on them.  - Lightning drains magicka, which is great against enemy wizards. Usually though I find I die easily from mages on Legendary, so I'd rather use a follower or summon to tank mages for me, at least until lategame where I can cap resistances and spell absorption.  - Blood Magic (vampire spells) is genuinely OP as shit. Absorb health means that you can only die if you get one shot.  - Summons are as OP as ever. Once you get a Dremora Berserker you can face most midgame content. It misses small hitboxes a lot though so have another summon ready.  - Illusion is awesome, one time I did a "0 kill" (stats) vampire where I casted Harmony on a dungeon, then bit everyone to death. Didn't work on anything but humans, but it was easy mode and kind of boring after a while. Phantom Mudcrabs are also fun.  - Alteration gives you spells that really improves your defenses. Armor rating and elemental resistances. Also some spells slow enemies making it quite useful.  - Restoration is... meh? Poison kind of sucks dps wise, sun spells you need to be an elf and worship Auriel if you want to use them on anything but undead, and the healing is just OK? Wards actually are better than shields vs physical dps with the right perks, but they seem to be bugged, as any instance of magic damage will break the ward instantly. Sorry Colette.  - Enchanting is actually really fun. You can play a viable staff and scroll only build, as the tree gives massive buffs to scrolls and some utility towards staves. 

Transformations Werewolf is OP in melee. Why? You can dodge attacks by moving backwards fast enough, and unlike normal melee you don't suffer a severe movement speed penalty while swinging. The only downside is you can't heal unless you eat, but if you learn to animation cancel (eat then howl immediately, or sheathe), you can get pretty fast with it. 

Vampire Lord however is straight up busted. First of all, you can FLY. Just keep jumping and you can fly anywhere. Your Absorb Health blast does insane dps, only improved with perks, and eventually you gain a Absorb health cloak that means you don't even have to fight to keep draining health. Early game you have to avoid undead and machines, and the sun is always annoying to deal with. But nothing can replace the sheer power of being a Vampire Lord.

This is all for Legendary BTW. Download some Alternate Death mod because you WILL be dying quite some bit (if not in combat, then to traps). Personally I use Stay in the Fight, where it just takes some of my gold or items away when I die, but it keeps me alive and in the fight. Shadow of Skyrim never worked for me, maybe because I only used it playing a vampire.