These are in ABSOLUTELY NO order, and get added as I think them up.
Post some of yours, and if I agree I'll add em to OP!
I would absolutely recommend a Blue response to some of the issues I am raising. As per my credibility, I have been a loyal fan for years.
1) Leah: No mention of her in previous titles, according to D3 lore has been there the whole time AND played an intricate role with the iconic character of the series (Deckard Cain)
2) Deckard Cain dies. Kill the face of the franchise? Bad idea.
3) "Breached Keep"- Messenger Martyn runs up, says his King doesn't believe in monsters, then runs into a pack of monsters as if they aren't there. He leaves through the keep, which it turns out is bursting with monsters. YOU LAZY S-O-Bs! Give him a death animation or leave his corpse at the entrance of Keep 1. WHAT HAPPENED TO HIM?!?!?!
4) Monk Inna's set 3-item bonus is .33 spirit regen. ONE THIRD OF ONE spirit. Thanks for nothing.
5) Holy Sanctum (Gardens of Hope tier 2): IS there some big secret NO ONE has let slip, or is it what it is? If so, good idea, poor execution.
6) Echoing fury always shows in my right hand in-game, regardless if it's main-hand or off-hand. LAZY!
7) How terrible the launch was, and the lack of features available at launch (PVP...)
8) Identifying/Salvaging- can you make this take any longer? Oh right. Originally it was 4 seconds to ID. EVERYTHING! If only you hadn't killed Cain, he could have done it for us... (See #2)
9) Collision detection: Once again, L-A-Z-Y you ain't got no alibi, you're lazy!. Trying to move around enemies is a joke, try escaping from fire chains mobs it is a big hinderance. But the most definitive proof is when enemies drop from the ceiling as in Sewers of Caldeum or Keep, or they swoop down from the sky. You run against an invisible wall even before the enemies have started to appear on the screen. Which reminds me of my next fail.
10) Unique/Elite monsters are given away by a glow even when supposed to be hidden. For example the Firewings or their kin in Act 3, or Sand Behemoths in Act 2.
11) "Buried" enemies are visible through the floor some times, for example if an Ancient Dweller is hidden on a bridge, he will actually appear down near the bottom of what you're walking on. LAZY.
12) Some cats in the Act 3 caves will not spring, though they are visible on the screen.
13) Some achievements cannot be completed (Shen has no "Victory" dialogue), and others are listed in the wrong acts (Magdha's Orders drops in Act 1 but is needed in Act 2 achievements)
14) DASHING STRIKE- If you don't know what I mean, you never use it.
15) Throughout the story the player's inelligence is insulted constantly- Azmodan gives away his plans, Diablo talks smack after every defeat, bla bla bla. If anyone has a good breakdown of every s#!77y part of the story elements, let me know.