I never used a syringe other than for healing from start to finish (did the last mission tonight. :-O~~~ )
I went down the same path you did, I've taken Sabal out and Pagan too. I believe there's various ways of completing these missions and letting them live, but for this play through I've gone all terminator.
TBH I thought there'd be more payoff of the story at the end, but maybe that's because I was a bastard and took out all the protagonists. :/
Just started the attack on Min's palace but had to abort because I brought the wrong load out, left the buzzsaw home.
I used to use the underwatery kits quite a lot when I was mopping up the loot boxes (I managed all but one from a time-limited level) and the berzerker one for occasional fun.
Yeah, that's not a mission that rewards subtlety.
I've still got a fair few hostage, assassination and hunting missions to do, so may do a bit of experimenting with the concoctions.
It's curious, but I've never had much trouble with Min's Palace. Maybe it's because I always play a really completist game, so by the time I get to the central mission climax I'm as well equipped as I can be.
I've always worked my way up the hill in a vehicle with a mounted gun for as long as possible, then gone off-road.
Don't forget to loot Min's body for a nice little Easter egg.
Oh I've got all the biggest and baddest on tap, but I like a bit of a challenge, so I swapped out the buzzsaw for an assault rifle before I knew what I was getting into, and brought the suppressed z93 (not especially useful), ripper SMG (very useful, but I reckon the spas will be more so), and the completely useless crossbow, will swap that for the one-hander GL.
Did you try shelling it with the GL from the buzzer first, or just charge in through the front gate?
I tried with the GL from the buzzer, but there seems to be a cap on how high you can fly in that area, presumably to stop you from flying over the top in a buzzer and shelling the place with the grenade launcher. I then tried hovering around just below the outer wall height and took a few guys out that way, but it was fairly banal.
In the end I stormed through the front gate, with the buzzsaw.
Did you both find that the ally AI was lacking somewhat? There were numerous times I drove away from a karma event or a liberated base and the golden path would literally walk into my vehicle's path instead of hoofing it away.