I would suggest the hunter would be the best to powerlevel with.

My gut feel (no practical experience of rogues or druids past 46 as yet) would be that the druid and rogue lack area of effect, multi target capabilities.

You wil be able to power level them but I think the hunter may be the most effective as it has better aoe and multi target abilities.

I've been boosting my druid and paladin from 32/33 through to 37/38 yesterday, mostly in SM with a few RFD runs. When I started I was taking targets down in 1's 2's and threes. It burnt them down quickly, but I wanted more speed. (I should say at one point I got sick of this then decided to try doing quests in STV). AFter the first 10 minutes killing raptors and completing one quest I decided that instancing was the way to go.

I literaly went into melee mode. I basically set the pet on a target, ran and hit the next mob and the next and the next and the next then dropped an explosive trap, and just let my pet and my raptor strike, go to town.

For the actual cathedral I would open the doors, and send my pet to the very end 2 mobs before the boss, then work back towards me picking up all the ones in the middle. (mend pet on). I would then run in and drop an explosive trap, and try a volley if possible.

If I got a load coming for me I would fight for a bit (it helped my pet heal itself more) and then I'd feign death. Throw a multi shot in there and explosive trap again if need be.

I would then repeat the process for the left aisle and the right aisle. Then I would clear out the left set of rooms and the right and burn down the boss.

I did try taking out the boss and pulling everything in the instance but that was a bit too much.

I was doing SM cathedral in about 16 - 20 minute runs, and was gaining about 22,000 - 25,000 xp per hour according to titan panel, not sure if that's good or not.