I've never had any issues with the DRV8825's, but then I didn't know about the 12% voltage limit until this thread.
I'm going to look into the different solutions. Until then you can try any of the approaches, and see what helps. The diode trick is probably the easiest to wire up and test, but the diodes can get quite hot - probably worth looking at TO220 packages as they are easier to heat-sink. Fast decay mode may help if you can get a wire soldered on to the pin - but that can be very tricky without a fine tip soldering iron and a steady hand. A4988 should work fine, but as has been pointed out you loose the 1/32 micro-step mode.
Out of curiosity, does the issue go away if you run the DRV8825 in 1/16th mode?
Another thing to try come to think of it is to use a lower supply voltage. If you have say a 9V supply handy (or something >8.5V), you could try AstroEQ with that. This will mean that 12% of the supply voltage is a smaller amount, so you may find it works better. Worth trying if you have one to hand.