To actually answer your question, since no one else did ... yes, there is one additional melee character you can get in Act 3, but he's not the easiest character to find. It'll be a slog to get that far without a tank.

Since you have a druid, you could try using a combo of animal form and summons to tank for you. I've found elemental summons are pretty durable, but won't do as much damage as a real tank.

Otherwise yes, you could respect a party member to tank.