Sudden Lag Spikes and Slowed Entity Movement after April 2nd Server Maintenance

Ever since the server maintenance on April 2nd of 2015, I have been unable to play minecraft 1.8+ due to extreme lag spikes every few seconds and unbearably slow entity (including player!) movement. Before 4/2/15, I got smooth gameplay on fancy graphics, maximum realistic shading, and 16 chunk view distance. Now the game is unplayable on every graphic setting, and furthermore graphics seem to have no effect on the constant lag spikes and slowed movement. I tried uninstalling minecraft and restarting my computer but nothing worked. I have the default resource pack, have not downloaded any mods, and there have been no changes in my computer that could have caused this. I am able to play minecraft version 1.7.10 or lower perfectly with no lag to speak of. Notice that I was also able to play 1.8 smoothly before April 2nd.