I would not be concerned with a Wrasse picking on a Sea Hare, but would be more concerned with how I was going to feed the Sea Hare to keep it alive.
A Sea Hare's typical food is not just algae but bacterial and other organic matter growing on the LR and glass, so after it cleans up everything it was brought in to do, it moves around more, looking for more to eat. This often leads to getting caught in powerheads and overflows, to pollute the tank and die. If that doesn't happen, it just starves and slowly fades away behind the rocks. This sometimes leads to another outbreak of nuisance algae.
To control nuisance algae in a predator tank I believe a better method is to keep the light intensity lower and use plenty of Activated Alumina to remove PO4. The low PO4, and low light inhibit algae growth so that animals are not needed for algae control. If this sounds interesting, I have 10 lbs. of Activated Alumina that I'll sell for what it cost me, $50. Please call or text 808-345-1049.
Aloha,
Mark