Tricky 11
We know from the harder version that it can be done using only climbers, bombers and builders. Thus meaning any solution that doesn't use any of those is fine.
Attached replay does use climbers, but doesn't use bombers or builders.
I think it's pretty commonly known this level can be done without climbers anyway, with a standard build-and-bash solution.
Therefore,
Tricky 11: None
Tricky 12
By direct drop, you can beat it with only one floater and then builders. Attached is a replay that uses all 50 floaters (therefore, 1 floater is required - it's pretty obvious that you need at least one of them), as well as climbers, blockers, bashers and diggers - but no builders. Therefore, the minimum for this is:
Tricky 12: 1 floater
Tricky 13
Either clam or CC said there's a solution that uses only 5 builders - fewer than this is impossible. Since the level can be beaten with only builders, the result is obviously:
Tricky 13: 5 builders
Tricky 14
Someone else can get this one.
Tricky 15
Very obvious - 3 bombers.
Tricky 16
1 Basher, and however many bombers are required when using the miner. You can do it without the miner, using more bombers, so the miner isn't needed.
Tricky 17
2 Bombers.
Tricky 18
1 Digger, 1 Bomber. You can either make the second lemming float, or make him build to delay him, therefore, neither is essential.
Tricky 19
If I'm not mistake, 1 climber, 1 builder, 1 basher, 1 miner, 1 digger. I suspect it's possible without any floaters, but I'll wait for someone else to confirm this.