Understanding double hot water return lines...

For years I was always under the assumption that each hot water return line needed it's own dedicated pump to the water heater. If you have two separate lines... you would need two pumps. I've seen some other plumber's work and they had two lines teed together before the single pump, check valve, then to the cold side.
It makes sense that it would work on the return part of the line, but doesn't sit right on the hot going to the furthest fixture part. Any ideas?, thanks.

I'm not a fan of attaching the return line to the cold inlet of a tank. Connecting to the boiler drain of the tank is what I prefer. I have never installed two lines on one pump and it would seem that one return would have a dominant draw over the other unless the piping was symmetrical in very way (length, fittings, etc.). A dedicated pump for each line seems the way to go unless somebody else in the forum has a different experience.

While I am not all that experienced with hot water return systems, the ones that I have been tasked with installing have all had multiple zones that are all serviced with one pump. Where the return line splits off to the separate zones, we install a throttling valve (many people use ball valves for this). Once the system is up and running, you adjust the throttling valves till all parts of the system have water returning from them. The more complex the system, the more trouble it is to get the system adjusted.

I've plumbed a few systems with multiple "zones" and one pump. Right before each "zone" tees in to the single line returning to the pump we put a "Circuit Setter".

I took a look at the Bell & Gossett circuit setters. Looks like that would work to overcome the imbalance of draw with one pump from separate zones. It also looks as of other tools are required for getting the proper balance that an HVAC tech would have for hydronic systems that I don't possess. I will continue to read more and educate myself. Thanks for the lead on the circuit setter, Hyper.
Link for PDF on B&G Circuit Setter: http://completewatersystems.com/wp-content/uploads/2011/05/583.pdf