Same here.

Have a good ping on all server 50 at 60 ms but disconnect every 15 min.

Have make a little test.

*Check the game via steam doesn't change anything.
*Restart with new character on normal/hardcore doesn't change anything.
*Restart Direct x (in dayz document) does not change anything.
*Change all the graphic on low, med , high, custom doesn't change anything.
*Change all the options too doesn't change anything.

A lot of player have this serious issue.