the way this hero rest worked feels highly unfair and not executed in a good way.
The main issue is, that players who have all 3 summoners can reset Avalon and Virion first and apply all XP cards on Elena, which gives an 65% XP boost at level 30 and an 80% XP boost at level 40. The skill which should only affect battles does work with XP cards as well.
After Elena is at the max level you can then reset her and get additional XP cards, easily up to 20 if not 30 million XP, which can then be re-used to level heroes way higher than they were before. 20M XP equals weeks, if not months of dungeon grinding and can completely destroy the balance of the servers.
The second (minor) complain is regarding the "free" skill reset. When you manually reset heroes, all heroes have their skills at 0 points. With this reset however, you get 1 point for the first skill. If you don't want this one, you need to add a second point somewhere else and afterwards reset for 100 linari or wait up to 3x 48 hours.