well one of the reason as stated above is in the old version we had to walk a mile ~ hour+ to get to the coins less combat, but now we are so close together, combat comes into play more often, so its now more noticeable
I always monitored/played the game since the begin and i never faced so high burst of blocks, except when f2pool halted a bit his power and then restarted
also not having a giant like f2pool to mine 99% of our blocks just adds even more randomness to the mix.
I think this is the main issue, or better there is low mining power and sometimes someone turn on for a bit his horses and BUM...
Or convince f2pool to come back and mine both algos again.