OK...if I change my Level 61 Druid into a Level 20 shroud. I then have a level 70 Cleric friend Power level the Level 20 Shroud in a level 40ish zone.....would my level 61 Druid gain experience just as quick, if not quicker, than root/rotting as a normal Level 61 Druid in Nobles, etc?
Is this a quick and easy way to level up from Level 61?

On a larger scale, if I took my friends Level 70 Cleric, made it into a level 20 shroud, PL the level 20 shroud in a high level zone with my lvl 61 Druid....would the Level 70 Cleric get exp at a good rate and get to Level 71 quick?

I don't think so. I tried shrouding down to level 30 and 3-boxing an LDoN once, and I hardly got any exp in the end.

Then again the exp system has changed since I tried that. You might have to try it to be sure.