Somewhere ind the Litecoin-Zeus thread Terry stated that WU has to be multiplied by 1.09 to get the pool side speed. But nevertheless it is really under performing. I also have such a dives...same config but is constantly performing 150kH behind the others 
I am guessing that you're using the diff. of 2048 as you said same config.
350 might be too high. Try 340 or try a different build.
Your rejects are high:
A: 593920 R: 26624
Mine look this after approx 12 hrs.
A:1067162 R:7752 WU:1507.6 Beta 1
A:1134848 R:1536 WU:1489.2 Beta 2
That's two different pools. Beta 1 or 2 will work on one pool. The other pool get a lot of rejects with beta 2 so I use beta 1.
Are you getting what people are calling a wall of rejects once in a while? That's what I got on one pool with beta 2. But beta 1 works on that pool.
Beta 3 was released last night: - Dmaxl's CGminer-4.3.5 Beta 3
Your rejects are high:
A: 593920 R: 26624
Mine look this after approx 12 hrs.
A:1067162 R:7752 WU:1507.6 Beta 1
A:1134848 R:1536 WU:1489.2 Beta 2
That's two different pools. Beta 1 or 2 will work on one pool. The other pool get a lot of rejects with beta 2 so I use beta 1.
Are you getting what people are calling a wall of rejects once in a while? That's what I got on one pool with beta 2. But beta 1 works on that pool.
Beta 3 was released last night: - Dmaxl's CGminer-4.3.5 Beta 3
What diff. are you using, and thanks for the link, I'll try it out.
Instant rejects with 440/2048, 440/1024 333/1024. Now trying 333/512.