I have the same configuration: dwa-552 and a dir655.
I have found no difference between the wzc and the dlink supplied.
A critical difference is "where the antennas are pointing". Even re-orienting them slightly makes a big difference. A movement of the router by a few feet also makes a difference.
Also check:
1. auto 20/40
2. wpa2 only (aes)
3. move all cordless phones far away (especially the base).