The reaper, as well as the bunker, had their build times increased by 5 seconds in response to the reaper bunker rushes that were popular late in the beta and early post-release. This also slows down the 3 or 5 barracks mass reaper builds that are now popular, but this only slightly weakens one of terran's many aggressive openings vs zerg. Center rax reaper rushes still hard counter hatchery first builds, which is the only thing that was unique about reaper builds. All other terran aggression, hellions, hellion drops, banshees, bio allins, tank allins, thor allins, remains mostly untouched. The balance problems in early game ZvT come down to the fact that terran is simply stronger and much more diverse early on, zerg has to rely on hard counters to have any chance to survive, but cant scout in time to implement them. Blizzard, by nerfing the reaper, only addresses one of the many builds terrans can do instead of the underlying problem and as long as they approach it like this the matchup will remain imbalanced. The tank's damage was also changed from 50 to 35+15 vs armored, but this is essentially irrelevant in ZvT, they will now kill hydras in 3 shots instead of 2, but hydras are not usable vs terran because of their poor mobility and ridiculously low hp. It also has a minor effect on zerglings and banelings, they now take 3 shots instead of 2 in the outer radius of splash damage, but the first and second radii are unchanged. As with the slight decrease in ultralisk damage, this will be important in some specific situations but is not something that is really significant in terms of overall balance.