It's been a while...more than 1 year. The game always changes and it';s always fun to play again! I am glad some suggestions made it into the game, that makes me happy!
Here are 3 more " premium" suggestions

) :
1)Add a tutorial. Simply let people choose heroes and give them max levels. Give some respawnable bosses, totems that show DPS,more in depth info on skills and the game and so on. this way you can test heroes more easily, but also help bring new players to the game.
2) Add game speed. After a friend showed me the trick, I play W3 with Cheat Engine. It let's you speed up the game. I usually play with 10-30% increased game speed, depending on the map. You could add a global buff that increases movement speed/atackspeed of heroes and monsters by a % percent. Depending on how the calculations work, balance my change . If it's too drastic, make it movement speed. If you and enemies would move 30% faster nothing would be lost.
3)add a shared life mod. Instead of each people having lifes, you have them in one place. Could help/reward team play and punish noobs.
4) Make the attribute bonus more interesting or stronger. Seems like you could so something with it. or just remove it...With the glyph ESC system putting points there is kinda meh, and very few people do it, only at end game.
5)Make the grunt a hero, so all things activate in single player, oh I see this is implemented! I suggested this loong ago
6)An option to remove tips ?
7) Disable monster kiting at healing stones. As a melle char you can position yourself to get healed while the monster just dies. Make it so he runs away in a situation like this or something.
8) Give ability to turn off items like flame grasp. Can be annoying with certain builds making aggro.
9)Show what items are part of a recipe, so people don't accidentally sell stuff. You could either have this written on an item, or show it when a certain skill is used on the item. Either full text " recipes 3 first row 2nd item" . Or something more simple. Just R3 R1 I2
10)I know you said a long time ago that you don't like it, but having items in a logical order would help a lot... Items are important and so much time is wasted on searching. Having " armor" " dps" " int" or any other list system would be nice,even if it isn't 100% perfect.
11) Enchant scrools. Some items can be upgraded to lvl 2, even 3. ALl you need is a scroll that drops from enemies. You could add a shop in the game where all upgadable items are shows, so people know what to except. You don't need to have a huge number of them,10-15 or so would be the perfect number + those that drop from bosses/mobs. This would add another dimension to the game.
12)If grunt dies, give players a chicken with 100 health. This way they solve all puzzles. ( I don't know if this is needed, no there yet and grunt didn't die)
13)Show total damage,lifes etc in the table. Also show % for DMG.
EDIT

laying the game right now, will add more ideas if they come to mind.