Your first suggestion having been proven only somewhat workable (depending on your server) you've moved on to the next step which contradicts your first post.
I'm just wondering if you've actually ever been crit by a magnus? I lost half my health instantly and didn't even have time to figure out where the actual summoner was before I was dead. Even at 80 with top jewels you will still take lots of damage from the pet while the summoner rides off because the pet control range is insane and they can direct their pet to attack while mounted. Bonus points on the off chance you actually manage