You could also try setting custom intensities for each card, separated by commas (-I 13,13,19,20). You can also use commas on other settings. I don't know the max temp of most of yours, but I do know r9 cards can take up to 94c and be ok (I keep mine at 85-88).
Intensities are already separated by commas

Cheers guys, I may have a play around when I have some time then.
One last suggestion, make sure the clocks are stable and not fluctuating a bit. Low watts can cause errors. I turn my 290x power limit to +10 when mining, and get as low as .5% rejected on some pools.
interesting, I know the 290 core speed does fluctuate ever so slightly, this is actually a common issue with these cards and it causes the card to drop off of bamt's ui. A friend of mine actually posted a fix for it.
what do you mean by power limit +10? is that a parameter in the config?
In MSI Afterburner, there is an option for "Power Limit." Double checking, I only have it set at +9 with my current clock of 960/1440. But yeah, when the clock bounces like that when at 100% GPU use, it's certainly low wattage. Upping this setting helps make sure it gets more.
My stock clocks were bouncy, too. Only have a 620w.