I think it's fairly easy on Normal, but Atheon on Hard is challening for me and and the groups I've been in.
Edit: After leveling to 30, I can kill Oracles in 5-7 shots with VoC depending on my distance, and as Relic holder I can actually dish enough damage to the Minotaur and adds to be consistent. As a 29 you can get one-shot sniped, or die fairly easily in the portal.
I run a lot of Raids to introduce newer raiders to the Vault, and as I mentioned before I also raid with 29's in Hard. It's not like I quit when we get to Atheon, we just never seem to get it done. The group usually disbands after some time and we are left with checkpoints. You don't need Hard Raid to get to 30, anyone can achieve it by acquiring Raid gear from normal and an exotic helmet. Hard only gets you the helmet.
So like I said I don't discriminate against levels, was just looking to complete these checkpoints with max-level team. I will still run normal raids with anyone, show them the ropes like I do every weekend and hope they get Raid gear and weapons. Many on here can attest to that.