-1, as some ppl already mentioned 15s is too less, if in case 2 good players are in a battle and are using a balance or maybe even a stall team, their matches can go for like 30mins+ and i don't think you can really make good decisions in such a heated match so quickly, it's not just about "clicking" on moves, there's a lot of stuff that comes into play which is impossible in 15s.
The concept is fine, just increase 15s to 30s-40s at least