Barbarian magic suppression skills...

Yes, in my opinion, there is only one useful spell that provides a benefit – Anti-Chaos. It’s very easy to disrupt a Warlock’s magic in this way; the ability that increases mana cost by 50% is quite effective, while a Warlock struggles with it. I don’t think it’s worth taking the other three spells, as they are not very effective against Light and Darkness, and Summoning is unlikely to be the main magic for a Necromancer or a Mage.