inside enemy land, let's say your 2 stacks are about to capture 2 cities, commando might be good.I don't know why a medic unit should need more promotions, although utility promotions that would be a waste for combat units (sentry for example) could be useful. I still prefer explorers. Their major drawback is that they have to receive the exp at training point, since they won't get new exp anywhere.
yet, i've never used commando as it's too late.
i mostly use a mounted unit with mobility+medic 2. i don't attach GGs much.