It sounds quite reasonable for the developers to nerf the summoning skills of Avalon, Virion and Elena, However, I think the way they do it is not suitable, fair or persuadable.
First, they are worried that some players only use the summoned troops into the back line, the weakest line of their opponents. However, preventing the players to choose the spawning location of the summoned units will make the fight less strategic (less work of the brain), but all about physical strength when two sides just crashed into each other, using all the devastating skills and the fight ends with the winning side is the one having more powerful and higher-level troops or heros. How boring! Moreover, doing so will make the summoning skill so useless and passive that no one will ever use it again. Then another question is that they created the skill for what when no one wants to use it?
I think the better solution is that instead of completely stopping the players from choosing the summoning location, they can prevent the players to summon only at the enemies' back line. Or other words, players can choose any where in their army's area to deploy the summoned units, not in the opponents' zone.
Second, they are worried that players only focus on developing the summoning skills without concentrating on building and upgrading their real army (and they want to reduce the numbers of summoned units). I can tell that the same situation happens to Jacques. While some players just focus on building him, the one-army hero, but the developers never touch him. That is really unfair. If you want to nerf the summoning skills, you should nerf Jacques, as well, AOC team! Or else just let it be.
Moreover, concentrating on just the summon skills will automatically result in less focus on other useful skills of the heroes. It means the players have to calculate carefully what to build to suit their play style when they have many useful options. Now that you want to declare death (yes, declare death) for the summon skills, players now only have some few choices and every one will build the same sets of skills for those heroes, which will make it even more boring.
In the final words, I hope they will re-consider it.