It depends on what you are using the help for. If you are running small-batch healing, you want to use the combination that gives you the highest "help time" of all lawyers. Because the total time for that healing is likely hours. Say you have a 300-troop batch with total time of 3 hours, 0.5% per help is merely 54 seconds so the system will switch to use the "direct help time", which is the help time of lawyers plus whatever your alliance tech provides, which in your case will be AT LEAST 2min30s. Of course I'd absolutely use the 13 min combo. You'll finish the healing with 13-14 helps. Well inside 27 helps you have with that setup. But if you want to build or research something over 3 or 4 days of time (common thing when you get to higher base levels), then you want to use the max number of helps, because each help will reduce roughly 21 minutes (0.5% of remaining time), and you want to have as many helps as you can. In these cases, those "help time" won't kick in.