I think the biggest thing I like about all the changes to casting is the synergies between different casters when grouped together.
Before it was just one caster relegated to specific roles no matter the caster. Having multiples was generally frowned upon as the roles overlapped.
Now looking at things. Imagine an enchantment archmage coupled with an aoe specced water or air savant. One holds while the other kills. This is quite a bit different from the old one holds and 5 kill methods of previous epics.
Got multiple savants in your raid. Let one do normal caster jobs like kiting handling trash etc while the other becomes a boss dps. This is even better if the savants are of the same element as the one kiting and can add to the dps of the other through awakening ticks.
A palemaster wails a large group of mobs and a savant follows up with some nasty dps to finsih off any stragglers.
Melees still have some roles here but it appears that it's just as easy to take a caster over a melee in many cases. I often take whoever for raids but this even more encourages that kind of attitude versus having 3 people join then swap off their casters becaues there already is one.
Granted there is always the chance that these situations become too strong and we end up with a time similar to when cap was 14 and melees where the odd man out.
With this many changes it is possible that we will see quite a bit of balance issues at the start and the pendulum swings pretty far to the caster side.