These items cause serious problems when equipped at the same time. The combination will permanently REMOVE 200 Health from all active minions.

This is easily reproducable. Simply have any summoned minions and a Hauberk of Life. Purchase a Sigil of Vitality. Not only will you NOT get 100 extra Health on your minions, but their health will actually DECREASE by 100 immediately. If you drop or use the Sigil, you won't get that Health back either. You lose ANOTHER 100 Health at that time.

Fortunately you can get rid of the Sigil of Vitality and resummon minions at the proper Health again.

I tested this with all Hauberk of Life, Sigil of Vitality, Twig of Life, Platemail of the Crusader, and Godplate. I only see it happening with the combo of Hauberk of Life and Sigil of Vitality. Everything else seems to stack properly.