You MUST use same hardware vendor (Mikrotik to Mikrotik) to get wds +wpa2 full compatibility.
Instead, you can use Ubiquiti to dd-wrt and vice versa (fully compatible).
Also Mikrotik (AP WDS) -> DD-WRT (WDS Sta + Mktik Compatibility on) works, but don't use wpa/wpa2 in that case (just problems).
This is a Mikrotik bug (or commercial try, why not...).
It's supossed we can get full wds+wpa2-aes compatibility between Atheros chips, but... This is not true in Routeros.
There is another hardware seller, "Deliberant", who says to have full Ubiquiti and Mikrotik Compatibility... I'll test equipments on June. So, then i'll posts results.