1: Overleveling.
A short story; I was faffing about with my team of guys in the early stages of the game, having just been severly dissapointed by the Lighthouse Boss, who used to be rather challenging in the original game on Hard, and how easily I beat him.
In my state of nigh-fatal frustration I accidentally headed to the Orc-Beach, rather than then Boar-Zombie-Forest-Thing. A zone 1-2 levels above me, something which I hadn't noticed at the time. And I actually started to feel challenged, possibly a bit too much so as I was legitimately struggling. Eventually it dawned on me that I was fighting level 7 crabs with a level 5 party and I realized that I was having fun because I, for once, wasn't overleved.
Later on, when I was doing Boreas, I wondered how the game had gotten so... droll, all of a sudden. Until I looked at Boreas' level, that is. He was level 12, my part - 15.
Fact is that level differences mean a lot in Original Sin and that the game, for some obscene reason, doesn't assume that you're going to be doing all of the optional content. Despite, y'know, being on Tactician Mode. And as such it it very easy to become overleved and therefore gain an unfair advantage, which in turn makes the game easier, which in turn is counterintuitive to a game-mode which aims to be Difficult.
In other words; leveling feels punishing, rather than rewarding. As it makes the game easier and in turn; less fun.
I therefore strongly suggest upping enemy levels, so that they actually match those of the player, provided they do the optional content. Yes, it removes the optional status from optional content.
But you were going to do it all anyway. It's Tactician Mode. You already know where to do up the quests and how to do them, if your here.
I will always be sad this game doesn't include an option to level-sync content up to your party's level. Even being a single level above your opponents makes such a noticeable difference in the difficulty of an encounter. Given the choice I would always prefer to remove that difference.
I asked for it even when D:OS was still in development, but people would always throw Elder Scrolls: Oblivion out there as an example of why level scaling designs should be avoided like the plague. Regardless, I would at least like having the option to enable syncing. Hopefully for D:OS 2, because I'm also finding Tactician Mode to be too easy, and it is largely due to level differences.