What types of law does the firm practice? Or, if they have a broad scope, what do they *want* to focus on? With so many specialized areas of law, that sort of broad targeting erodes budget quickly. No good generating a lead from that keyword if that keyword already has a bloated CPA, even worse if that lead’s not something the firm is particularly interested in or equipped to handle.
If your landing pages/site are decent, DSAs are a better way to mine for new keywords while still driving some quality traffic (assuming you watch ’em, apply tons of negative keywords – though you should already be doing that, and set usable targets for the campaign)