Yeah I see that ... its the same for me. You notice that the Pool difficulty is not varying but increasing.  Based on your screenshot you just restarted and miner and having small shares.  First the pool difficulty start with 16 and you could have very high WU even higher than hashrate.  When it stabalize after few minutes to difficulty 128 and above the WU seems max out at 90% of Hashrate.  

Below screenshot is R9 290 Elpida.

--no-submit-stale --gpu-vddc 1 --gpu-fan 100 --gpu-engine 1000 --gpu-memclock 1500 --thread-concurrency 24000 -g 1 -I 20 --worksize 512 --gpu-powertune +20 --lookup-gap 2



It seems to me modded Vertcoin-CGMinerAleks_NR3 is more stable than buggy vertminer-0.5.2.  Verminer after crash cannot restart fresh like cgminer and need reboot Windows.

BTW vertminer options need to change --scrypt to --scrypt-vert