As a Marauder I only have reliable intelligence and dexterity from the special +30 nodes. So I'm not looking to cast anything at max level, low level should be good enough. I also play hardcore, so no point in suggesting town portal on-death casting.
Normally I don't cast any non-melee spells and don't know anything about them. But it might be good to have some of them. Ideally I'd have two who are good on both kill and damage taken, I only have experience with strength spells.
On damage taken: Molten Shell,
Abyssal Cry, Totem (mostly Decoy Totem), Summon (Flame/Stone) Golem (bonuses apply to the player)
On kill: Warlord's Mark,
After testing more I've found a lot of these spells aren't being cast. I'm not using vaal skills or reserved mana skills or supporting them with anything else. One of the skills is too high level. But Rallying Cry isn't and I can still cast it manually, so clearly it's not being supported by the on damage taken.
Apparently war cries can't be cast through these types of support gems.
And it doesn't work with totems either.