QUOTE (tisoz @ Feb 25 2020, 12:46 AM)

I personally have always been uneasy about Great Form Spirits using their Powers outside their Domain. I think the ability to be able to Summon Spirits beforehand and put them on standby until needed is a huge advantage. The magician has time to rest and recover from any Drain, they save Combat turns during a fight, and they can control to a great extent where they are summoned such as a Home Ground or one with minimal Background Count. Just these advantages make Great Forms worthwhile. Allowing them to use all their Powers in any Domain sounds like how the RAW work, but it seems like letting a Sea Spirit use all its Powers in a desert is broken.
While this all *can* be true, I don't believe it is often the case.
Syd the Summoner, has Conjuring 6, Charisma 7 (to match the one the OP mentions), and is a Grade 2 initiate - not a starting character, not massively powerful. He's summoning in his back garden, a nice background count=0 sort of area...
Without InvokingThey want to summon a Force 3 spirit - roll 6 dice (conjuring)+2 (grade) vs 3s = 4-5 successes probably. Because the spirit is <1/2 charisma, they roll their 7 dice vs 3L, easily soaking. Fair enough - force 3 is not bad, but they have lots of services. A F3 spirit going up against trained / elite guards is going to struggle, but against pedestrians or mall cops, will work nicely.
They want to summon a F6 spirit - roll 6 dice (conjuring) vs 6s = should statistically get 1 success. Spirit is < Charisma, so the drain is 6M - so they roll Charisma (7)+ Grade (2) for 9 dice vs 6s - and they will probably get 1-2, and take a light stun. No worries - only 10-15 minutes rest probably - so they will be good to go soon.
As soon as you move up to invoking through, the odds start to shift.Force 3 spirit, great formed = Conjuring 6 vs 3s - 4 succseses. Drain is still 3L on 7 dice - so no problem. But then you need to make the invoking test - so Conjuring vs 2 X force-grade, so 6 dice vs 4s, needing only 1 success - so that's almost certainly fine. Now for the drain - it counts as F4 (force X 2 - grade), so it's over half charisma now, for a drain of 4m. Still 4 successes on 9 dice should statistically happen... so we're all good to summon a flock of F3 great form spirits. But again, while they are now awesome at dealing with a whole bunch of pedestians, by the time you as a character has invoking+grade 2, you're probably not worried about that as a threat level.
So, let's temper this down, and only go for a F5 great form instead of a F6. First test, we're rolling 6 dice vs 5s, so should get 1-2 services. The drain is 5M on 7 dice - so we're probably taking a light unless we throw a re-roll at it. For the invoking, we're testing against 8s on 6 dice - so as long as we get that 1 dice that *should* on average be a six, and then don't roll a one, we're good. But the drain is now 8S (F5 X 2=10, 10-grade 2 = 8, the force is now >charisma, so it's an S drain, the normal force makes it stun, not physical) Now we have 8S drain on 9 dice, so we're probably going to get 2 successes at most, and take an M. Now Syd the summoner is on M+L or 4 boxes of damage (1 from the first test, 3 from the invoking) - so we're talking 60-90 minutes of complete rest to get rid of that.
So sure - if you give an invoker half a day, he can turn up with 4 X F5 great form nature spirits, and that will ruin a lot of parties. But he's also spent 6 hours trying to get rid of drain, during which they've done nothing to contribute to their team, and needed to rest fully. Surprise that same summoner with a combat, and watch as he summons a F5 but then is on +2 modifiers for the rest of the combat from summoning drain, and really has to hope his 1-2 services are enough. Until you can get to Grade 4-5, and bring the invoking target numbers back down to something more manageable, you're not going to be running around with packs of spirits like a mage will have from his elementals. And by the time you do - you're probably facing packs of Shedim, Drakes, Free Spirits, Bugs or Horrors that require that kind of magical mojo to make it a fair fight.
All during this, our Summoning 6, Charisma 7 Hermetic, has had 7 F X6 fire elementals that they summoned last month and have LONG since drained, on standby and ready to mob stuff in combat. And they'll still be there after dusk, when the team have to delay their assault for Reasons™. While the poor shaman hits dusk, all their hard work vanishes, and they have to start again - and now a 6 hour delay is unacceptable, so they have to make the tough call of how many spirits, for how much drain, and how much stun to go into the fight with...