And for solo xp + endgame RvR groups...

Theurg / Cabba / SM / Skald / Hero / Eld / Enchanter?

I am looking to abuse water pots on the casters to extend into the water because most people don't buy water pots in the BG's

I think caba, sm are fine like solos in rvr and pve.

I'd say Theurg or Skald. Both can get groups in RvR and both can solo xp.

Skald spec is fairly universal, and theurg I would level with Ice, although Air is probably better for BGs but not so great leveling.

Both have speed, which helps in BGs. Both are great BG soloers.

Cabby is good also as dots wreck most players in BGs due to low resists and stun or disease pet for kiting/interrupting them as they die. And of course the focus pulling. No speed kind of sucks though.

When I've encountered groups about to run me down in BGs, I use the water as well. I know I'll go down due to numbers, but most of the time there's at least 1 or 2 idiots who swim to the bottom with me and can't make it back in time after I'm dead. You still get rps if you've damaged them beforehand and you don't release.