Ok since it's Weil McLean I'm guessing its a indirectly fired water heater. Do you have a separate boiler? The pipe on the bottom looks like its the supply to heat up the water heater for the indirect water heater. If that pipe is leaking you'll have to shut down and drain the boiler and replace the pipe and fittings where its leaking from. As to why its warped again I've never saw that before. If its not leaking that's good haha. I'm sure someone else can chime in and may have an answer for that.
Actually took a second look and it may have warped due to the leak. The insulation probably got wet and and now the outer shell, must have been leaking for a while is my guess just maybe not noticeable till lately.
I don't think it an issue unless it is leaking, however when the plumber is there get him to inspect the heater and make sure the heater itself isn't leaking. Obviously if the heater is leaking then yes replace it. Also avoid mr. Rooter, they charge a lot and usually there guys aren't all that qualified. Just do a bit of research and see who does good work in your area. Some of those companies who charge flat rates to do the work tend to be expensive, I used to work for one and our prices were outrageous.