Another mechanic that annoys me, is the knowing that there are a limited number of drops of Pharros Lockstones and the fact that there are totally some keyholes that only exist to troll you.
Pharros' Lockstones are completely unlimited. Join the Rat King Covenant, and you get one every time you kill an invader, which is actually pretty easy because that area is positively designed for ambushing/setting-up invaders. I'm pretty terrible at PVP, and I achieved Rank 3 in that covenant in a matter of hours at level 75. (I burned some Bonfire Acetic at the entrance bonfire to beef-up the rats, too.) I have over 30 Pharros' Lockstones. Yes, some of Pharros' mechanisms are sort of useless (like pools of healing water not far from a bonfire, or the pool of poison in Earthen Peak ... if you don't know to destroy the windmill to stop the poison) but that just reinforces putting thought before action, which is the crux of these games.
Something else that bugs me is that leveling up is now 2 load screens away. I don't get why they don't just let you level up at every bonfire.
Yeah, this is poorly-designed. With unlimited fast-travel it feels like a huge waste of time to warp to Majula every time you want to level. The Emerald Herald also repeats herself too much, and how many lines of (the same) dialogue before you get her menu? 3 or 4?
My complaints are definitely fast-travel, and enemy AI during co-op. If I summon 2 players for a boss battle: it's always an assured victory, and summoning has definitely been notably easier and more frequent than previous Souls games. Both bosses at Heide's Tower just kind of pivoted awkwardly, seemingly trying to figure-out who to target, while we surrounded and beat the snot out of them; it felt positively broken. I like that boss HP scales with the number of players present, but the AI should improve as well; maybe there should have been specific multi-player boss attacks.
Weapon/Armor durability is also a joke; all equipment magically repairs itself at bonfires, so what's the point? I've almost never had durability problems with my equipment, except in areas with enemies/hazards which degrade equipment durability, and even in those cases: a bonfire isn't far away.
Someone also said the areas feel disconnected, which I feel is also an affect of the fast-travel mechanic. I'm more than half-way through the game, and I don't remember how I got to all the areas, nor do I remember how they are tied together; in Dark Souls I quickly had a grasp of how the areas fit together.
It feels pretty easy, but it's hard to tell if that's because I've put so many hours into the previous games, or because new mechanics are negatively impacting the difficulty.
I also don't understand why we're allowed to re-spec character stats, but can't re-design our character's physical appearance; character stats directly influence game-play and game-balance, but character design has absolutely no impact on game-play. I eventually got sick of designing my character (the designer is too involved and convoluted) because I wanted to play the game, but players should be allowed to go back and fine-tune if they want. Hell, I have 3 Soul Vessels, yet no present desire to respec, but I'd love to try to make my character less ugly ... or more ugly.