What is cruelly lacking is a solo mode with especially a scenario, a captivating story in several chapter spaced according to the updates, it would allow to know a little more the heroes their past and their future, with enemies again , boss, and hero evil.
Another suggestion would be duel implantation only in the allied realm, in order to allow to train and find the right combination and strategy between friends and allies.
A system of selling the inventory items would be interesting, many objects in the inventory no longer serves anything by advancing in the game and accumulates.
Winning a little more endurance and mana potion would allow you to stay a little longer in the game instead of playing 10 minutes and turn it off in the absence of potions or decreasing mana recovery and endurance to have them available quickly.
An improved cash shop with attractive prices on different items (skins, emblem etc ...) and diminishing objects that unbalanced the game, it is often the richest or those who spend a lot of euros wins....alas.