Nothing wrong with RDM's aggro- their burst is just really, really high. If RDM steal aggro from you, ask them to pick up diversion or use lucid dream early. With all cooldowns up, RDM bursts around 6k worth of enmity on a single enemy. AoE shouldn't be running into issues. If they're still stealing after pull, like on a boss, consider doing another rotation of enmity gaining skills before dropping into DPS.