Nothing is "hop-proof". But, in this case PPLNS is the next best thing. By design there's a ramp-up period (3 days in this case) where you don't reach full block payout potential until after you've been mining for 3 days. If you know you've got to put in that much work before you see your "proper" payouts, you're less likely to leave in-between to seek luck elsewhere, lest you've lost most of your past 3 days' worth of work.
From April 5th to April 8th you would have seen payouts increasing since that was your ramp-up period. Then in the past 12 days we've gone from 304 miners (4/8) down to 267 miners with the most recent block today (woo, another one 2 hours ago!), so in theory you would see earnings increase there as well since there are less shares from the other miners competing with yours.