You talk about trip being useless because people often use two round lag skills, which go through just before a trip, effectively meaning the trip doesn't lag them.

How about this for a solution?

Instead of tripping as often as you can, wait until one round after they used their two round skill, then trip. That way they can only do that skill every three rounds. Or if you feel you can time it right, wait until two rounds later and beat them to the punch so they can only do it every four rounds.