The reason for limiting summons is not for performance reasons, but for balance reasons. The more characters on the player's side, the larger the advantage they have. Enemies only usually get 2 "standard actions" per character. If they spend those actions onto a disposable summon, which only costs AP to summon, That is a victory for the player, because it's actions not spent attacking them.
This is one reason why Summoner is considered a powerful archtype. Those Totems are all weak, but when properly placed, they either stick around to add extra damage, or the enemy attacks them, wasting their own actions for a totem which you can replace the next turn.
The "horde of summons" wasn't as unbalanced in Diablo 2 because it was a different game, it was a battle of Horde vs. Horde with no limit on how many actions each side could take other than health and mana. In DOS 2, each encounter is fixed and limited to only a certain number of enemies, and the amount of actions which can be taken is strictly limited.
It would require a very careful design to make a horde of summons not unbalanced in a DOS-like.
Last edited by Stabbey; 19/08/1812:32 PM. Reason: Diablo 2
