So I've just recently returned to the game after a very long break.
I've decided on focusing more on running older content, etc. But at the same time am looking for a class that is relevant for current content and in a good place. I would more likely be DPSing in current content.
However, its been a long time since I've played a Death Knight, this was during WTLK. And I don't have any experience with a Warrior besides the one I am currently levelling.
Which class is good at soloing old content, i.e Vanilla, TBC and WTLK dungeons/raids? Also which class is looking in good shape for DPS in 5.2? Also I plan on queuing for a BG when I can, how do both classes stack in PVP?
It's a tough choice to be honest. Both are doing really well in current PvE. As for soloing old content, DK's are traditionally the kings of soloing, but to be fair, Warriors with Second Wind are pretty amazing at soloing stuff as well. Basically as long as Second Wind can outheal the damage you're taking, and there isn't some crazy mechanic that resets the fight or whatever, then Warrior should be able to solo it.
I'm not very good, and I was able to solo quite a lot of stuff as Arms DPS. Would probably be even easier as protection.
Also bear in mind that there are no DK sets pre-Wrath, so if you like soloing old stuff for transmog sets, you might have more fun on a Warrior.
As mentioned, it's a tough choice, but I'll stick with my warrior no matter what, and here's why:
Warriors remains as one of the top DPSers, along side DKs as well. It's more of a skill thing than a class thing.
Older content (Wrath and down) has been made very easy to solo by Blizzard due to some of the bosses dropping companion pets. Do note, not every boss is easy to do as a warrior, but Second Wind makes it a whole lot easier.
In general, a warrior can solo everything a DK can in TBC and up to Trial of the Crusader. I haven't tried ToC that much, nothing there really tickles my fancy, but I've done everything up to that point, including OS 3D 25 man.
Blood DKs however do some amazing things. Their damage is pretty high, and they basicly never die if Death Strike is used correctly.
Level them both and test things out, but keep in mind; with high gear a warrior can burst pretty much everything down before it gets the chance to kill that said warrior.