Heals, for all this regular content is irrelevant- we already have too much healing power. The damage, is going to be a little funky (like in WoW) but a clear difference is in WoW with timewalking lower levels are scaled up. Here we are only scaling higher levels down, we don't need to touch the lower level that much. Potency of the higher level kit would be curved down, so that it is 'roughly' right. That is why I mentioned potentially if you took a complete level (say) 30 kit and compared it to a level 100, the potency would lightly favor the level 30 BUT the features of the level 100 would make up for it. Also baring in mind that the level 100 is probably bringing max ilvl while the new player is not.
This is easier than WoW's situation cause in WoW people are going both directions. Here we're really only focused on smoothly curving people down. I also think this is much easier long term then trying to set up a good kit, and then not mess up that good kit (like they do) each expansion. So I believe creating the best as reasonably possible curve is a better, more stable, long term solution than anything else.