given recent events, which firms have best dcm groups?

With the Leh/Barcap merger, I'd say they'll definitely be a force to be reckoned with. Leh has/had some of the best power/natty res and fig dcm teams on the Street. I haven't looked at the league tables in awhile but I think they are pretty high up.

Barcap has also been traditionally strong in credit/debt (for the most part, their U.S. IBD biz was mostly DCM with a sprinkle of coverage and such. They laid off half their lev fin team earlier this year)

Depends what region you are talking about. In Europe, Deutsche is no.1 according to league tables and I think in Asia, HSBC is no.1 and Deutsche is no.2. JP Morgan and Citi continue to very strong DCM teams in the US. Barclays has had a very good dcm desk too actually. They were mandated on quite a few deals in Asia and Europe from what I last remember. Overall, for DCM, these banks are usually lead mandates on most deals:

Citi
JP Morgan
Deutsche Bank
Barclays

IMO I don't think DCM and ECM are good places to be. DCM probably worst right now.

Depends where mate. When I was working over the summer in Asia, I saw good deal flow. But my US colleagues told me the deal flow was pretty slow.