I'm not saying it can't be done, but I have to say that there IS a problem with a "Swarm" or "Hive-Mind" design to a champion. That problem is, MOBAs, while obviously inspired by the Real-Time Strategy games of the past (The whole GENRE came from the DOTA mod of Warcraft 3 after all), they ARE different game types.
Real-Time Strategy games revolve around controlling multiple, usually large armies of units at one time. Certain maps of the storyline campaigns of those games would give you certain "Hero" units, usually empowered versions of existing units with increased stats or the occasional exclusive power such as a Magic Spell, or some other ability/power.
However, MOBAs lock you into to the use of ONE character, essentially locking you into those "Hero" units, and the regular footsoldier type units you build at the Barracks or Training Facility of whatever races in a RTS game, are not controllable.
If you don't understand, let me put it this way. For all intents and purposes, those types of characters, the ones you call "Hive-Mind" types, at least I think in a MOBA, are an example of a "Minion-Mancer", or a type of champion that summons creatures, and then use said creatures that they summon for additional effects. This type of champion/character or whatever you want to call them, I personally think are as close to a "Hive-Mind" type of character we could probably get.
along with 
and 
are, to the best of my knowledge, the main champions designed in this fashion in League of Legends.
summons Voidlings which he directs through use of his other spells.
plants her Seeds, which create additional units dependent on what spell she uses to activate said seeds.
creates graves via his passive and Q, and then summons Ghouls from said graves, directing them to targets with his skillshot E.
Note, that with any of these 3 champions, that there is a way to affect, or direct the actions of the units they summon/create, but they CANNOT be controlled DIRECTLY BY THE PLAYER. The player can INFLUENCE the actions of those units, but not control them directly.
TL;DR: MOBAs just aren't designed for the control of multiple units at one time.
is a rather unconventional example of a hive mind. She absorbs everyone who makes an oath to her.
