Why is a lobster capable of killing a crab, which costs 1600 metal? This damn unit destroys the balance. What is especially stupid is that the jack gets a double jump, breaks the building and runs away. Turrets become useless

I would argue that widow is also able to kill crab in some circumstances. The question here is how preventable and how much counterplay this unit allows. Widow is easily defeatable by escort.

Multiple lobsters and flying jacks need counters that are very metal-expensive, much more than widow-counters are. I agree that there needs to be some sort of clear counter to lobster if we are operating in rock-paper-scissor game still.

Cheap (to be cost efficient vs lobster), huge DPS (to deal with the lobster before it can throw the crab), all-terrain (to reach a lobster thrown at a crab spike).

Gnat?

I would be cautious of any sort of flying counters, because they tend to get shut down awfullly easy as well.

My alternative of Gnat is either Venoms, Knights or Racketeer. Knights are probably optimal. Not cheap, but is worthy to have regardless as a generalist.