For the Druid, it's best to develop Chaos magic. If you have anti-magic, that's great. There are some spells in the Castle that might be useful. For example, Lightning or even Disintegration. This is, of course, in the best-case scenario, but it's still better than nothing.
Life magic is also good, but not against Chaos. Nature can also provide some good buffs, and a couple of combat spells definitely won't hurt the Druid.
A second hero could be a Barbarian. Why not? First, focus on developing magic resistance for him.
You can also hire a third hero. You complained that he's a Rogue. Hire one too; the Castle allows it... They can operate independently. But others can advise you better on this topic than I can...
But you can also make the second hero a Mage. Then, it's better to develop Nature + Life magic. This diversity will also be useful.
But your main trump card is anti-magic. The hero must be able to withstand it. If this spell is not available, then the second magic skill for the hero is canceled. Develop magic resistance – this will be the Druid's second skill.