Vanilla Diablo 3 had serious issues, and despite the core gameplay being solid, there were issues with balance there as well.
The team kept nerfing great tactics, which made the game less fun.
Fast forward to now. I've given up on Destiny for largely the same reasons I gave up on Diablo 3. Hearing that D3 had improved since Vanilla, I picked up Ultimate Evil Edition.
WOW. THIS is how you make a loot game. GOD DAMN it's great. Classes have been rebalanced to reintroduce fun builds that challenge you to push into higher difficulty levels to see what you're actually able to handle. Overpowered builds suddenly start to show holes in specific situations. Other builds become viable all of a sudden. Loot is plentiful, but not everything is a legendary. Getting great loot is still worth celebrating.
My biggest problem with Destiny's loot is a serious problem with how they built the loot tables. Here's what I mean:
In Diablo, from every level from 1-70, there is gear that appears in the common, uncommon, rare and legendary tiers. A good rare at 65 might finally replace a legendary you got at 45. You lose that cool secondary ability the legendary had, but the rare just has better base stats. Tough decisions need to be made. Suddenly you're not sure if you want to upgrade, because it's not an upgrade across the board. You gain life per second, but lose the ability to summon a ghost to fight by your side when you kill an enemy.
Destiny's loot tiers are based on levels. After Level 15, you will never get a green that is worth your time. After 20, no rare is worth your time. Now you can ONLY get legendaries to upgrade. Rare guns cap at 242 damage. No blue weapon will ever be an upgrade for you once you have appropriate gear for 20. There is no other option. There are no tough choices. There is only either crap, and direct upgrade. Suddenly, just by seeing the color of the gear that dropped, you know it's useless to you. There's no suspense. There's no excitement in maybe getting an upgrade.
This is exacerbated by the quick leveling. 1-20 goes by in a flash. You spend very little time getting direct upgrades and interesting variations on gear. Once you hit 20, your focus is largely singular: legendaries (or exotics). You also only have 7 (one entirely cosmetic) slots to fill with gear, instead of Diablo's 13. That also limits your chances to find an upgrade. 6 slots to upgrade, and only one tier of loot that will ever be an upgrade for any of it. That limits your choices really quickly.
Bungie needs to sit down with a game like Reaper of Souls and see how loot should be balanced between drops, crafting, and mysterious unidentified items.