It's an okay fight .
Spread out, focus on one mino at a time at all costs and you should be okay.
If I recall correctly I was using battlemaster's menacing strike repeatedly (which then, with careful positioning and a tiny bit of luck, would cause AoO and buy my team some time), using duplicity from Shadowheart to give advantage, then either having the Gith do the same thing as my PC (HE Fighter - Battlemaster) or use Wyll / Gale to do whatever they could in terms of damage. Usually, at that point, it would be something like hex + scorching ray while having advantage or scorching ray, grease, mm, ray of frost whichever really made more sense.
Once you drop one mino it's just a mixture of baiting the mino into wasting effort into killing off your casters and then using aid.
