Any race can play as any class; what others consider to be the "best" combo is purely a subjective matter. That said, in terms of "min/maxing" or placing yourself in the most optimal position to take full advantage of racial passives, you certainly did quite well in selecting a Redguard. Your reasoning is sound; Redguards are great for stamina builds due to their innate passives. I'm actually surprised you haven't seen a DW Redguard NB--that's a very popular and powerful combination. Still, always remember that just because you might see a certain type of build more often than another doesn't mean that any build can't be viable. It's best not to worry about what other people think; do what suits you best and play the game the way you want to play it.

As for your role, yes, you fit the description of a DPS or Damage Dealer. Medium armor and DW are excellent choices for a stamina DPS. Definitely buy all the medium armor, DW, and Redguard passives, as you unlock them of course. You want to spend most (if not all) of your attribute points in Stamina to maximize your DPS output; putting some in Health is fine, but I wouldn't waste any in Magicka as it would just detract from your damage potential. NB ability-wise, use anything that has an available stamina morph. Here are some good skills/morphs to pick up: Rapid Strikes (morph of Flurry, DW skill), Steel Tornado (morph of Whirlwind, DW skill), Ambush (morph of Teleport Strike), Killer's Blade (morph of Assassin's Blade), Relentless Focus (morph of Grim Focus), Shadowy Disguise (morph of Shadow Cloak), Surprise Attack (morph of Veiled Strike), Power Extraction (morph of Drain Power), Soul Harvest (Ultimate, morph of Death Stroke), Consuming Darkness (Ultimate, either morph), Werewolf Transformation (Ultimate, if you want to be a WW, gives 15% passive stamina regen while slotted).

For PvP, you're likely going have trouble until you reach higher levels, especially if you're trying to take on more than one opponent. Run with a partner or a group if you can. If you like flying solo, that's fine too, but you have to be a bit more clever in fights. Sneaking and cloaking are two things Nightblades do very well. If you are able to catch enemies off-guard, that will certainly work in your favor. PvP combat requires a lot of quick thinking and maneuvering in and out of sticky situations. Try to use abilities that stun, snare, or trick your opponents. Make it difficult for them to hit you. Don't be afraid to look for an escape if things get too hectic.

Hope that helps

Redguard has a lot of stamina abilities, good choice for stamina builds. Have at least one skill from each of your three branches on your quick slot so you level up all 3 of them at the same time. If I were you I would go all stamina in stats. Easier to use heavy armor but in the long run you'll want to use medium if your not going for a tank build. You can reset stats and skills with a bit of coin. Luring with a bow and duel wielding weapons is a popular choice for pve.

If you really wanted to, at level 15 you can still equip a secondary healing staff on your self, doesn't really matter. Either way try things out as much as you want.