I can't comment on tactician as I've not got far with my Durge tactician run yet, but I will say that on normal I found the big fights where enemies were able to stop my party healing (like the House of Grief and the basement during the raid on Moonrise Towers) by far the hardest. But while those took me a few tries to survive, on the whole I found the combat on difficulty reasonably consistent, or at least varying within limits that I found challenging but achievable. I wouldn't want it to be too same-y.
But I agree that too much inconsistency isn't fun. It really bugged me in WotR, for example, that I felt I had to keep tweaking the difficulty level to progress (though am willing to accept that possibly I just sucked at playing it). I'd found BG3 so much better in this regard, but I'll reserve my judgement until I've completed my tactician run.
