There are a lot more factors that contribute to winning a skirmish or team battle, mainly because each hero is actually manned by a player who can do anything for whatever reason which may or may not be a detriment to you. A guy might not feel confident committing due to being punished early game, another guy might have a flash of inspiration and juke an entire team, another guy might fumble controlling a secondary unit making himself vulnerable for a second. There's a lot of fuzziness to Dota 2 compared to Starcraft 2 which is far more surgical and precise. The fuzziness can serve to obscure one's shortcomings (if you fear getting shouted at, or just mute everyone), but also gives that satisfaction of constantly learning something completely new (as opposed to refining execution) and after a while you'll even start anticipating "random" elements just by intuition.