The game's very hard bots (5v5) uses cheats to regain health or make skills become available faster. Unfortunately they are hard-coded bots, so performing an event that confuses the bots will lead to victory. I'm not sure if a learning AI will be able circumvent this problem--we will assume it does, since the 1v1 bot was able to grow out of dead-end thinking.
The 1v1 learning takes about 10 min per match. A team of 10 people programmed this bot, and who knows how many matches it needed to play to achieve such a master level. They could have been working on this bot for a year. 5v5 ranges from 20 to 70 min per match. The time it would take for a team of bots to be proficient would take 2 to 7 times longer than a single bot, based on time of match and assuming the same number of trials will achieve such a high level. I doubt that 10 people is enough to create a beast; they would probably need a team of 50-100 behind the scenes to create super bots. We have not seen 5 self-aware bots coordinate something. I bet they will run into some messed up confusion and be looped not being able to determine a decision. Look at the Youtube video of 3 AI talking to each other; someone managed to get Siri, Alexa, and the Google Talk bot to be in an infinite loop. Now, if it was 1 bot controlling all 5 characters rather than 5 individual bots, I would bet on the 1 bot.
Even so, I'll still bet on humans. Humans have outsmarted robots in the past with creativity. These bots have been learning by throwing eggs at walls and seeing which don't crack, rather than tholinking critically. Of course bots will always be better in terms of raw numerical calculations, but we have not seen a bot with the ability to derive Einstein equations yet.