Caelum questions, both themes.

[Liadran]

First about research as Nagot Gick Fel said Harab Seraphs are faster researchers. If you (as is mostly done with Caelum) add Magic scale to that, then you're research is a bit faster than base Caelum can go with (base Caelum Seraph is also faster than High Seraph.

With Harab Seraphs you also get undead leadership. That's not to be forgotten with them. Also their paths are not useless if you think about the troops they are normally used with. Nagot already pointed out one good use for them. But if one says that only usefull spell is Orb Lightning then you haven't checked all the choices there is. That earth pick is very usefull for early expansion. If you go on item usage, then it's much more powerfull (they also can use Rain of Stones and also reserach it quite quickly). Ironskin as said is a very good spell (as are some others). It's not that uncommon to kill unarmoured mages.

Spring Hawks and etc rituals can be cast by Harab Elders as well as High Seraphs. For construction you can more easily get Dwarven Hammers. You only get 1 more air gem/turn, so not much more air rituals for base Caelum. Too much lighting use can backflash later in the game (can be defended against, and everyone will expect it). Storm is as effective for Raptors as for base Caelum. Quickness is missing and it takes some firepower away, but Raptors are not designed for combat lighting firepower as base Caelum is. They have more strengts elsewhere. Elders are Capital only which means that you have less of them, but Harab Seraphs used well are far from ineffective (they just are not lightning throwers). In longer games upkeep is quite important thing. Raptors have lower upkeep and it counts for quite much. Also the better aproach for no supply and no upkeep troops is an important matter. And the fact that Raptors are better at hurting enemy economy is very important.

When you start you can (with patrol) buy few Elders already. It also saves money if you consider other ways than Mammoths for early expansion.

Raptors synergy with their magic comes with their troops, not only with combat spells. Air, earth and death must all be used to their full effect. Earth can alone fix some of the flaws of Caelums' troops.

About that Dominion. Raptors can't push their dominion as effectively as base Caelum, meaning that where the figth is there most propably is not a Cold +3 province (and you don't have Wolven Winter for easy use).