I remembered wandering around the south/south east section of the map when I just got to the island, and my dudes were level 9. After a brief trip through the graveyard, we went out and got jumped by assassins (since you already mentioned running into these guys, this shouldn't be a spoiler). They were level 12. You can guess what happened next. Saying they mopped the floor with my team would probably be an understatement. The guy who went first, he totally wiped us out within his turn.
I was bitter, yes. I had to reload and avoided them while swallowing my pride. But I swore I would come back and get my revenge. I was a bit worried whether I could get strong enough to overcome such odds within 3 levels.
Those backstabbing snakes were my goal for a while. After 3 levels, I came back as promised. After a really good fight, I put them back in their place. It was a tough, but good, fight.
But anyway, my point is, I feel your pain. The game could get trying at times, since running into a fight beyond your level, getting wiped out and having to reload is not such a rare thing. And the Reaper's Coast is a dangerous area. However, the fact is that depending on your progress route and strategies, the outcomes can vary widely. In my playthrough, level 12 was basically the milestone beyond which the game never really got out of control anymore. If I happened to run into a bad fight, it would be just a matter of adjusting my tactics.
Granted, I never minded the whole "item hunting" thing. I think it was because, while I might have to spend half an hour to hunt for a few good items for my team, it always felt so good and worth it, that it never really bothered me. Any good items I managed to get my hands on would always prove their worth in future fights. It was like that until the end of the game. You could say I'm one of the lucky few who manage to adapt to the system.
Having to hunt for items in shops frequently to keep up with enemies, especially on Tactician, is an issue that has been discussed over a lot. Even though I wasn't particularly bothered by it, as I said, I would still like to see an overhaul of this aspect in a future patch or the enhanced edition - if we have one.
You know, I have no issues in finding a though fight and having to return later to get my revenge - in fact, I love that, is the mark of a good RPG. The thing is, I feel like the progress of my characters is decided only by my skills with the traders and not by my conquests and experience.
I clearly remember, in DOS1, getting a 1-handed club from the Keeper of the Lighthouse that was amazing for my tank (because tanks actually worked there) and I had it for many, many levels. There's nothing like that in DOS2, because as soon you get a good item, you'll be replacing it the following level, if not sooner. Having to constantly scroll through endless lists of items from vendors is not fun at all, and probably the most anti-RPG feature I've seen in a very long time. Amazing items should come with a great story behind, yet I can't remember where I got each one of mine, probably from Kurt the Apple Pie Vendor. That's friggin' epic, uh?
I have to say that this strange way of playing the game has sucked out any will of keep going. I can't even force myself to load it again because I know that, as soon I finish the next fight, I'll be stuck again against extremely buffed enemies and I'll be shopping endlessly.
Fort Joy was cool, flawed but eventually fun. As soon you get out, the game just goes downhill, and it makes me very sad.
