How did you level your tank?

[Machka]

with only 3 cross class slots at my current lvl should I take voke over convalescence?

I'd recommend Provoke, Mercy Stroke and Convalescence. As already mentioned, Provoke is essential later, and helpful even in low-level dungeons. Mercy Stroke is free damage - since leveling dungeons have several packs between bosses you can get a lot of use out of it. Conva in the third spot means you have it as inc dmg starts ramping up in dungeons.

Note: if you like big pulls, take Conva (and even Foresight) before Mercy Stroke. The extra healing and mitigation helps big pulls go smoother. I usually skip Bloodbath on DRK b/c the self heal only procs thru physical atks. All DRK aoe dmg is magical, so Bloodbath's effectiveness is greatly reduced. (It can be useful on some fights later on though, so take this with a grain of salt.)

Eventually, you'll want Provoke, Convalescence, Awareness and Foresight. Can fill with Mercy Stroke or Bloodbath as you see fit.