For the Bard: On lvl 7 i had trouble to kill blue mobs, while all points were put into weapon...good luck solo-lvling a bard. maybe it gets better once u get the first real dmg style. I didnt bother waiting, finding groups is easy with healer-classes. Same for my duid.
I lvled Hero and VW mostly solo to 50 both was easy. Guess its the same with Champ and BM. BM might be a bit slower.
Animist: No question, maybe the easiest of all.
Casters: No problem until lvl 25-30. After that it becomes slow, cause u cant kill OJs reliable or very slow and have a lot of downtime due to mana reg. Manamentalist is a bit easier due to ae-dot farming.
Ranger is easy aswell...albeit boring, atleast for me.
NS: Never tried, lvled my Animist only on spots with xp loot and saved the loot to bring the NS to 50.
Dunno how it is for warden.
The highest p/hour farm solo can be done with Animist.
For best overall farm u need either a Bomb for DS / HoH (rr4+)[other chars can do DS/HoH too, sure, but every group runs with 4 bombs, so its easiest to get a group with a bomb] or any MDPS/Bomb/ani/Healer/tank for Hulks in DF, dependig on the setup.
For what u described, the mana mentalist seems to be the best choice: Good lvling with ae-dot. wellcome in most pve groups due to red hot and pot, great RP in zergs with the ae-dot. And when u want to do some DS runs: Respec to light, do some runs and then go back to mana. With the new changes, even a mentalism spec might be valid in a energy dps-train. And the caster-template is cheap, which might be important if u are new on Hib or on this server.
For melee: A Hero is fine. Good to lvl, wellcome in many pve-groups due to guard/protect, wellcome in Zergs, since casters wont get interrupted by gtaoe spells if close to a full tank, wellcome in small and 8man as peeler. And u can play the tank in DS/HoH, but u should get one or two trainings-runs with ppl who know what u need to do.
have fun