This is one of the potential and likely side effects of VU Cycle Steal. It is not compatible or useful in all games.
Jake Stine (Air) - Programmer - PCSX2 Dev Team
VU Cycle Steal doesnt work well with DQ8.
AMD Phenom II x3 720 @ 3.5GHz
ATI Radeon HD4870 1GB overclocked
4GBs of DDR3 RAM
Nearly any game you use VU cycle steal on with "moderate" or higher you'll have this. Some games (like katamary damacy) will have massive slowdowns even with it set only to "slightly" on some levels. This isn't a bug, it's just the nature of the speed hack.
Dark Cloud (the first) works perfectly with VU stealing set to moderate, If that matters at all
Intel Core i5-4690k @4.5ghz
Samsung 16GB DDR3 @2000mhz
GeForce GTX 680 4GB
Windows 7 x64
it might just be the games I have played, but I haven't really gotten an increase worth note on games like P4, FFXII, Soul Nomad, and SRTZ so I just don't use it. The other speed hacks are more useful, so is trying the newest beta or revision of gsdx.
Intel Core 2 Duo PM8600 @ 2.4 GHz
4 GB DDR3 1066 RAM
ATI Mobility Radeon HD 3670 512 MB
AMD Phenom II x2 550 (unlocked to 4)@ 3.5ghz
4 GB DDR3 1600 RAM
Sapphire 5770 1GB