Respect, just DPS her down faster than she activates her power. Odds are it'll be close but if you're really struggling she's vulnerable to... one status ailment, never went out of my way to test it though so I don't know what that is. Reverse, she has a lot of HP but not much else, it seemed to be a pretty normal fight to me. In my case I was around level 50 when taking on all those fights, if you use level up eggs you should be able to reach higher; but on the other hand I had all orbs released up to tier 2, so that's likely a factor.
As for poison, I have no clue on how to heal it, luckily I just never got it early on in a relevant fight so I haven't had to worry about it. It does suck that there doesn't seem to be a way to get rid of it though.
I like how they handled most of the game quite a bit, with the notable exception of level drain, which I think should be reworked. You lose a level and no matter what fight it is or how they stole the level, they get fully healed. This makes level drain just unfun in boss fights and trivial to deal with in random encounters, I wish it instead increased max HP and healed by that amount like the original, just preferably with a scaling factor so it's not just +500 all the time even once you deal 2k+ a turn. I wish the damage increase was also tweaked down in turn, because as it currently stands easy fights become hard and reasonable fights become nigh impossible even with just a single level drain, as opposed to the original where if you set it up right you could basically get levels sucked as much as you want without the fight becoming adamantly impossible.
I like the scene variety in this game more than the games before it, overall. With every character having a paizuri scene suddenly there ends up being a lot more variety for the rest of the scenes. Also find it funny that Hard Succubus is going to be stronger than Grand Succubus now. ...Hard Succubus will come in version 2, right? She's coming back, right?
In my case I've beaten everything in version 1 and get to look for the bits that I've missed, namely 8 remaining medals, getting the out of combat Daydream Tower and max dependence scenes (haven't touched these yet because I've been sticking at 0 dependence due to how you couldn't return to 0 dependence once you've lost in the original), and getting that elusive king that's supposed to show up in various places. Does he show up in the same area in the first forest area as santa did in the first game? Or somewhere else? And can he spawn if I do battles in the same map, or does it have to be a different one? Finally, what am I supposed to be able to do to the scarecrows? It just says all of them are abandoned when I check them.
Edit: lmao, I wrote all this and forgot to ask my main question. What are the conditions for a brave battle with bosses? In simply playing through the game I got 7 of them, and based on the achievement listings it seems I'm missing 3 of them, presumably for Alraune, Alp, and Sayu. Going with what the side wall leading up to Alp said I tried refighting her starting the fight at above 50 lust, but still no dice. It seems to be visible from the start of the fight, so I'd imagine it's some preparation thing, but I'm not sure.