So I too have noticed a significant improvment in how long it takes to ping. and the funny thing is... i have not updated my phone yet (still waiting) im currently getting readings as follows: 
WIFI 
11.56 mbps download, 
11.96 mbps upload, 
71 ms ping, 
NETWORK 4G: 
6.56 mbps download, 
1.53 mbps upload, 
86 ms ping.
I ran it twice for each at different times and all results were similar, which is crazy because just two weeks ago i was in the 1000s. so T-mobile must have done something, and it obviously wasnt the update