I contributed the max for HSA but didn't use HSA distrib to make COBRA payments, can I deduct COBRA pmts on sch A as well as my HSA contribs on line 25 of 1040?

Yes you can ... just because you have an HSA doesn't mean you ever have to use it . 

If any of the HSA contributions were made through your employer, that deduction has already been made through your W-2 (code "W" in box 12), so that will NOT appear on Line 25 of Form 1040.  Only HSA contributions that were not made through your employer would show up on Line 25.