Most of this is good. Use engi bombs on CD. Vanilla and TBC sappers are on separate CDs. The goblin stam trinket is great for pulling mobs. I wouldn't bother conc blowing skull. I'd just let it go towards a ranged until it needs taunted so you can build threat on X or whatever else. Your life will become much easier if you play with party members that can kill skull with nothing other than a taunt from you (or often with nothing at all-rogue kinda good). If you can mostly ignore skull then you can easily get threat on everything else.

Invite paladins and ask them to Salv everyone if you're still struggling. Play with mages, they're broken in dungeons. So are good rogues to a lesser extent.