Strange, lost my post when starting editing it... luckily I saved it.
Here is it again..
Hermit Yoda can be used at very low gear level. Mine is still g11 (while my other JKR team members are reliced). And I had him pretty long time in my JKR line-up with g10 only. And he always dies / flees last. He has the ability to stealth (and got 100% evasion when in hiding! No worries about aoe attacks). And with good speed mod, he can almost stay in hiding through the entire match. Also he has no attack skills, so no worries about counterattacks.
GK on the other hand needs to be high geared and modded beefy to be useful. I would say you need him at least on equal gear level of your opponents. Because he's a tank and mainly there for absorbing punches. There is some support utility with his mass cleansing and call to assist attack. But if he can't survive when he taunts (and he taunts a lot), you won't be able to make much use of his support skills either.
That being said, a good JKR team does not really need GK (anymore). Actually, a good JKR team has no much use for any taunting tank, because you have revives provided by Jolee. GK is much better nowadays with a Padme team. Hermit Yoda on the other hand can bring much more to the table for a JKR team with heal, foresight (so they can also stay alive after Jolee's revive) and turn meter boost. Also with Master's Training (which is an awesome buff), you also get a mass assist ability for free. Get your Hermit Yoda in and replace Old Ben. You won't regret it.