Server: Mob pathfinding induced massive lag in any versions 15w49a and later

Any snapshots I've tried to run on my server after 15w47c have been unplayable. Massive block lag with just a few players on. I've been terribly busy and have not had a chance to report this.

Is there a secure way to upload log so only Minecraft Devs can see it?

Here is a sniplet of it.