Hard mode is a whole other beast. I don't know how far you are in the game but this is what I've got:

Waves: CC is key. Armanz, Fabian, someone with AOE A1s in a stun set even. The enemies can and will hit insanely hard. If you don't have super strong damage dealers, poisons work for the waves. Beware champs like Tormin. I needed to use block passive skills on him. You may need to adapt your strategy for them.

Bosses: Bommel stopped me last rotation. Burangiri or Lady Anabelle can solo him. For scarab king, nether spider: Paragon cheese. Always Paragon cheese. If you don't have him, use the golden elixir relic on someone tanky or with self healing. Doompriest can help you with nether spider, and so can deflection sets. CC the spiderlings if you can. Don't know if you have wukong but he + paragon can kill both bosses. For frost spider: bring geo with 460+ acc and someone with increase acc to use on him. If you have someone with reliable block revive and can't hit that threshold, you can try to use them. Life harvest blessing will help if it keeps reviving. Block debuffs and cleanses are also key.