I don't understand at all. Does map hacking also play a role there?

Knowing your opponent's choice (I won't say how to do it – many people know, and those who don't, don't need to) significantly increases your chances of winning. In other words, in TC3, you need to choose a tactic in advance – for example, take a Berserk with a vulnerability sphere or a specific set of troops with specific skills. The number of options is limited; if you know in advance what your opponent will choose, you can adjust your own choice. For example, against a Berserk with a vulnerability sphere, take an anti-Berserk amulet (well, that's a bit of a cheap tactic) or water magic – you have very good chances of winning. The only thing you can do is require the champion to make their choice first.