Oh God My Eyes!
I feel your pain...

Summoned animals should under no circumstances be made into a herd. This ruins the whole point of farming. Not only that but summoning such a large amount of creatures as well as their upkeep would be too draining for even the most powerful of summoners. No one person can focus their concentration on controlling10 creatures at once never mind 50 or more.
If something is summoned it should 1) only last for a limited amount of time, depending on the summoner’s skill. It would be draining to keep a summon alive thus they cannot last forever.
2) Summons should not be able to move very far from the summoner. Thus you cannot summon a creature and have it chase your opponent for great distances while you walk off in the opposite direction.
3) Summoned creatures should NOT give fighting experience, drops or anything else for that matter since this is basically begging for power leveling. Summons are meant purely to fight for the one that summoned them. Perhaps also for the testing of a new weapon or spell, but definitely not for training.