2 360 rads is more than enough for your components, and having them all in the same loop is fine, order doesn't matter either...if the pump is poor, then you may not be getting the head pressure to keep the flow rate at an acceptable level. 0.5 gpm is the bare minimum you want, 1.0-1.5 gpm is great. Apart from all of that, have you made sure there's no chance of airlock by rotating and tilting your case to remove any trapped air, or tried reseating the CPU block? (yes I know that it'd be an absolute pain in a hard line loop). Also, what is your airflow setup like, and do you have any means of control for the pump speed?
If you're going to end up replacing any blocks, make sure that what you get is aluminium as getting any copper/brass/nickel plated parts will cause corrosion, even with inhibitors...
