easy way to tell if someone is instant reviving... The timer actually works in this manner. There is a 1 minute cooldown from the time your battle starts until you can revive to hit again. If the round goes longer, you have a shorter cooldown. If he is gaining in damage dealt at a faster rate than once a minute, then the player is using instant revive.

As far as the rounds go, I have seen smaller players consistently stay higher up in rank than what their power leads to beleive possible. The main strategy in these events consists of formation, runes and gear sets. If this player is using a well thought out setup then it is definitely possible for him to excel in these events.