How did I stop you? :p Heck, if you roll badly, I'd have let you try to sneak behind him!
Obviously Soorec was going to have some defenses, because of what the party did last time (actually, he managed to get his hands on defenses that time too) but really, his ultimate defense is that he's the chain that holds the grak-graks in check, not the mind that keeps them going. It's kept him alive (or at least ressurrected) through three generations of cultists, and unless you have a good plan to take advantage of the chaos that ensures (that is no doubt useful) he might be happy to take the gamble knowing you guys are unlikely to survive. And that there's always some kind sucker ready to ressurect an innocent seeming gnome
Being unlikely to survive is not quite true, I think if Ameena and Petal can roll well, they could acrobatics (tumble) well enough to get clear and run away, but I think the rest would die. If you actually do an all out attack, I think Haynuus and Petal can deal decent damage, but Ameena is hampered to support without items to use or clever tactics to employ, the NPCs are useless, and I can't see it not being a party kill /party massacre that way either without some very good tactics on your side. And you aren't potioned up nor prepared for the assault right now
It's always an option, just note narratively the hooks I usually give you to play around with and outway any inbalance in combat (and to actually make it a real fight that flows from the narrative and back out again) are against you this time. They wll just pile on the damge not caring about themselves, and then will tear your corpse apart so dead is dead until you get to a VI altar (assuming you can get all the bits).
Anyway, all this warning is perhaps moot, given what Haynuus just sneakily did
Obviously, as you are getting close to the end, you need to work out what it is you exactly want to do. Rescuing Ameena and Helm is fine, but what you have of coruse is a dangerous opportunity to get close to the upper command of the blackskulls and also get some information about what is happening. Clearly, you guys moving around is bringing thigns ot a head that did not happen before. Clearly attacking Dolo caused something that Soorec used in his favour, but just as clearly not finishing the job and killing the priest means he needs you guys for some reason, btu is also anxious not to be away for long. Until you know what those circumstances are, best not to assume that getting back quickly is not more important than getting you guys. Also, realise he seems to act on whims instead of needs - look at how quickly he turned on Falkor.
Ameena is obviously set on finding parts of the Soul Stone to call back the Grey Lord. So you obviously have to work out if this is a good plan, and what needs to chance (or if things have changed) well enough that it doesn't go wrong like las time.
And oviously, Petal and Deephold know only as much of that as you've told them.
.
. Also bear in mind Ameena is in the arms of one of them right now - if she thinks she has a chance to suddenly squirm free and leg it, she'll take it, but she's not gonna try if she doesn't think it's worth it. She's sort of limited to just her hearing right now, as far as senses go - she has her eyes shut, her whiskers are surrounded by grak-grak, and her nose is pretty full of it too, though obviously she can pick up enough nearby scents to at least tell that her friends are nearby. Besides that, all she can really do right now is listen. and if it comes to a fight, grak-graks are undead so she can't Sneak Attack, and she knows what happens is Soorec is knocked unconscious/killed, so she won't want to be doing anything to him either (not that she'd try to actually kill him, even if she had the chance). On the plus side, her combat damage isn't affected by the loss of her latest knife, since the damage it did was the same as her unarmed damage, and she is always considered to be armed anyway as she has the feat...Improved Unarmed Strike, I think it's called. I think she can also do Sneak Attack damage while unarmed too since she can choose whether to make her unarmed damage lethal or non-lethal. But that's sort of irrelevant right now as she doesn't plan on fighting anything 
