This is exactly why I stopped bothering with debuffs initially (later on you have access to more that seem to work, and one character in particular seems to be only good for debuffing and healing) on fights where I was slightly below, or very below the enemy levels. AFAIK it's not solely based off of your spellpower stat, but also your level compared to the monsters, but I could be wrong about that.
People go on and on about how awesome Sylvando is in combat, especially for his crowd control abilities. Even at ~420 CHA I have to disagree somewhat. He's great at group healing, and I also found him to be a way more reliable source of the Oomph spells compared to Veronica, because he's way more durable, but I haven't found any of his CC abilities other than Fuddle Dance to be useful at all. And even that only seems to be pretty good on equal level or below trash, but not bosses. His AoE spells don't seem to do much damage, and while he does have one CHA skill that does nice single target damage, it's not enough to warrant the MP instead of saving it for a heal or making sure your melee characters are Oomphed if they aren't yet.
But anyway, I actually took a somewhat early detour and went somewhere way out of the way where enemies were much higher level than me. It wasn't too terrible until I ran into a group that kept constantly pepping up and doing combo attacks and they kept calling for backup. So by the time I was able to actually kill one of them, they had just called in another. Debuffs didn't work at all, and I think it literally took me ten minutes for that fight before my party got wiped out (fleeing just wastes everyone's turn when it doesn't work, and it seems to work less than 50% of the time). It also seems like if you aren't at least equal level to the enemies (and sometimes even when you are) that they always get to attack your party first. I have agility rings on everyone too and whatever agility skills I could reasonably get. I once ran into a group that went first, but not only did they go first, they seemed to get an extra attack or two. There were only three enemies, but they got a total of five attacks before I could go. On top of that, they kept casting a party wide lightning spell that had a chance to paralyze. And it did. Fun times.
It sounds like when you posted you were still relatively early in the game too. You end up getting a party heal not much farther in after that boss. Also, I don't really get the "bosses are easy when you know their gimmicks" replies. Well duh, just like any game, but you don't know them until you stumble upon them. I also haven't been grinding, and only one boss took me more than two attempts to kill on Draconian. For the desert boss in particular, it didn't take me even six turns, but I guess I kind of "cheated" since on my second attempt my entire party was pepped up, and I also actually discovered what one of its weaknesses was on my first attempt, but it didn't really seem reliable due to the uncontrollable AI that kept interferring. The reason it seemed so ridiculously hard to me was because on my first attempt it literally did a desperate attack or crit for 235 damage twice. No one in my party had close to that amount of health at the time. Similar crap kept happening with at least half of the other bosses too.
I can't stand them. It's especially annoying when an enemy can cast one that hits two members at once, or some that are party wide. What's even worse though is that in some games where you have access to similar skills, you don't even get any experience when they work. Not sure if you do or not in this game though because due to the low success rate, I've only used it twice. Once was on accident.
You mean magic blocking spells that you often can't even cast until after the enemies have already cast them? It's funny when you learn that an enemy has that ability, then when you next encounter them swap in the character that can prevent instant death, only for that character to be killed with the spell before they can block it.
