RPG Summoning/Conjuration Balance

So I am designing an open-wold RPG and I consulted my friend about the logistics of Conjuration; them being you would have to have essentially a "down payment" on the initial summon, and the "regular installments" to keep it alive.

In relative terms, the initial summon would require a varying chunk of mana to instantiate the creature into the world. Subsequently, a portion of mana is drained per second for however long you can manage to sustain it. Alternatively, you can un-summon the creature at any time; at no cost. This is practically just like Skyrim, but there is no time limit and the emphasis is on how well you as a player can sustain the creature as opposed to the level requirement, summon time and mana requirement involved in a system like Skyrim.

The point of which we ran into trouble was deciding whether it was balanced or not. I made the points that you would have to be more conservative and skilled in your strategies, since you would have less things to do with less mana available since it is constantly being drained. He said you can just drink mana potions and negate the exhaustion. I affirmed that it was true, but asked what relevance it had to do with the strength of the already summoned creature. He then replied with how you would be practically unable to reach the caster if they just use crowd control spells and abilities. I said that is dependent on how well the caster executes said spells and abilities, and whether or not the player has perks to mitigate cc. I also added that an archer archetype would be a prevalent counter-pick, since a caster build heavily invested in magics would lack any of the substantial physical defense whatsoever to survive an archer's barrage.

He started referring back to how much of a nuisance an extra enemy would be to deal with. I made references to 2v1 PvP scenarios and Annie's ultimate with Tibber's in League of Legends and how a player opposing Annie would typically run away and wait until the threat is gone. He said that the summoner would be useless if enemies could just run away. I also included that her ultimate had a 45 second time limit, required only a one-time mana cost and is most effective when the enemy player had just been stunned and most importantly was that Annie could still cast other spells and do other things while Tibbers was summoned. Then I asked him why he thought it was so overpowered and unfair if a player could simply just run away. He kind of just told me to "ffs deal with your own damn problems i'm tired" and went to bed after that.

So I'm just curious: IS there a way to have a balanced summoner archetype?