Where you walk and it's all SURPRISE: BUTTSEX now kill these 5 rabbites.
This is more along the lines of what I was talking about. Not actual random encounters, but the enemies just appear either via teleportation or digging up from the ground or flying down from the sky. Like Ankhegs in BG1, and Cliff Chasers in Morrowind. When you're trying to get somewhere in a hurry and then you've got to stop and possibly die because you didn't see these guys. This kind of thing is perfectly alright in a horror shooter, but in an RPG it tends to piss me off. I'll be running low on health due to a dungeon I just left, forgot to save, and a wimpy little turd with wings will manage to kill me.
And the sole reason I stopped playing turn-based (and also random battle) RPGs is because of the backtracking part. Especially when there's a sudden ramp up in difficulty...case in point: Legaia 2: Duel Saga (which wasn't very fun to begin with, I thought it was gonna be more like the first one). There's a part where you're in this volcano fighting monsters that can kill you in 3 rounds if you're not careful. And then you fight the boss(es) who have 89,900 and 92,000 hp at the same time. The previous boss had only 55,000 hp. So after you realize that there is no way you're going to survive this fight, and that you need healing items, you have to walk all the way back out of this dungeon which can take up to 45 minutes without the some-battle-avoiding item). And then grind.
A lot of those RPGs tend to do this. I'll have fought every battle I've come across in the game, and maybe an extra 50 or so on the side for good measure. And then I'll come up to an enormous dungeon in which the designers put a boss expecting the player to have done nothing but grind for around 10 hours after the last plot point, find out the hard way, and have to go back out again to get healing items and just grind around for a bit.
While I'm at it, sudden ramps in difficulty. Star Ocean 3, you get to Styx, and the average enemy HP jumps about 20,000 or so. Which is just fucking stupid. I've sat through half-hour cutscenes and fought every monster in every dungeon at least twice to try and get better equipment, and they throw something like that at you. Had to grind for at least 5 hours in the moonbase just to survive my frantic dash to the exit while hopefully avoiding the enemies.