I have had wifi problems on my older BB Key2 phone. It was even 2 times in service centre due to disconnections and they said everything with phone is OK. I have changed 2 wifi cards in my Omnia. Then I bought Unihertz Titan Slim (yeah, HW keyboard is a must for me) and it has overall wifi problems, which their support had to solve and its firmware was totally untolerant with 802.11w setting - comparing to Key2, disconenctions were every few minutes.
I dont know, from which version of TOS, 802.11w is present, but after setting it to disabled - all my home wifi problems were gone.