Generally, I'd agree with Bobby, hit a lob yourself (or your partner, in this case) and come on in...even if it means you have to retreat to chase their return lob.
Another tactic, if you can pull it off, is a heavy slice or drop shot...as I think it's harder for your opponent to hit an effective lob off of that incoming shot. In addition, it might bring them
...and again, it's harder to hit an effective return lob from inside the service line. Having everyone at the baseline just invites a long rally of groundstrokes.
But I feel (and know) your frustration. These are the most
types of opponents to play against. They try your patience and stamina...since their game is predicated on keeping the ball in play and waiting for you/your team
to make the error.