Honestly, stasis isn't that great/powerful. It gives you a 20 turn window to attack/build where your opponents cannot do the same, and is only really useful in the very early game.
A 20 turn window on turn 100, for example, is really meh. Your opponents already have vast armies, so either your army is strong enough to take em on (in which case you don't need stasis) or the enemy will not need additional troops (blocked by stasis) to repel your forces because they have a massive army anyway.
A 20 turn window in the first 30 turns can allow you to build a few extra warriors which are still pretty meh if you consider that you usually need more than a 2:1 attacker:defender ratio when attempting to warrior rush without aggressive or some other early war mongered ability (like the hippus worldspell which is simply beastly).
From my experience, Stasis is best used to build a settler and research an extra tech, making your start up to par with a high difficulty AI start, which is a good thing in and of itself, but not amazing.
As for Samhain, that ritual is one of two things, either:
a) You shoot yourself in the foot by building it early, wasting valuable early
that could be used on warriors/workers/settlers, and once you do build it, your defenses are undermanned
because you built it and your position overall is significantly weaker agianst your own frostlings, to say nothing of your neighbors.
-or-
b) You toss a bunch of
into the trash can because you didn't build it early, seeing as at anytime past the early game, frostlings are nothing but free xp for all of your enemies since they will have large armies easily capable of routing said frostlings.
Edit: Why is this ritual in the game in the first place? It seems like a waste of space that does nothing but hold the AI back.
To be honest, none of the above seems annoying for a non-illians player. Stasis early=30 seconds of pressing enters and grabbing lairs/goody huts with scouts. Stasis later=either 5 minutes of building improvements or 10 minutes of war mongering. Meh, not that bad. Samhain early=crippled Illians. Samhain later=Illians wasted a bunch of hammers. Again: meh?
There is one important caveat to the above, that is if you are playing on marathon (or maybe epic) speed, in which case stasis/samhain can be annoying. However, I am of the opinion that given FFH's already reduced speed, playing marathon is like playing an entire game with stasis on anyway. Or quasi-stasis if you prefer
.
My point is, if a tech requirement is introduced, stasis needs to be doubled in length because honestly, when compared to other worldspells (such as the ones held by the hippus, lanun, elohim, grigori or even the balseraphs to name a few), stasis is not that good.