Without the Jedi, they still have good leaders (Rex, Cody, Thorn etc.) and excellent tacticians (Tarkin, Yularen etc.). Yeah, I think they'd still ace it.

I think the ultra-powerful combat wizards do give the GAR a slight upgrade.

^True. The Confederacy had some gooduns: Trench, Grievous, Loathsome.

At first the clones suffered heavy casualty because of the jedi. But as the war went on the jedi got better at commanding. So i think the GAR is better with them.

I think on average the GAR's performance would fall off without Jedi.

Some units would improve, obviously (any unit previously headed by Krell, for instance) but on the whole they'd drop off a bit.

Technically the GAR wouldn't even exist without the Jedi, as they were originally ordered with the purpose of eventually wiping out the Jedi