I used to work at Wendy's as a Hamburger cook. Wendy's Burgers just have salt on them.
Wendy's burgers come in big sleeves about 35cm(i'm guessing 14 inches) x 10cm x 10cm. The main thing that makes Wendy's Burgers different is they're square. They're not like Burger King for instance which are all pre-seasoned/pre-charred in some factory. I had a friend who worked at Burger King who told me "we used to just microwave them" At Wendy's the meat is just plain hamburger meat. One of my managers joked "what makes Wendy's patties special is we don't cut corners"
So, what happens is you take a patty out of the sleeve. The sleeve is contained in a metal drawer. In the drawer is a sleeve for quarter pound patties and 8th pound patties. I'd have to wash my hands constantly because they were often covered in blood. Normally you'd slit the plastic sleeve up the top and pull patties out individually as needed. You also had to watch the temperature of the drawer and the little mini fridge below. I think the fridge was kept at 50°F or 10°C
You put it on the grill and you season it with salt from a salt shaker. 30 seconds later you flip it. Then you press down on all the corners of the burger starting with the lower right corner. Much blood will come out. You do this once and only once because you don't want to contaminate the burger. 60 seconds after this you flip the burger again. and 60 seconds later you flip it again. Now you flip the burger at 30ish second intervals until it has reached the proper color brown. This is variable. Also to note. The grill at Wendy's is on a slant. The slant is only like 3°. It's just a sheet of metal. So, it drains the grease and blood out of the burger as time goes on. The grill is very hot. It is heated by gas below it. Sometimes it was fun to make flames on it. Also, throughout the day you use salt to clean it.
The burger is placed on a bun and mustard is applied in a W shape. Ketchup and Mayonnaise are applied with a knife from troughs. Vegetables are applied to order. I did the burgers and fries though. I only worked at the sandwich station twice. When I worked there Wendy's fries were just plain potatoes. While working there they changed the type of oil they used. Which didn't make much of a difference in flavor. But after I was working there, they changed the fries completely to the sea salt fries we have today.
I have several times made home made Wendy's style burgers. I worked there for a year and a half between 2005-2007. If you follow the steps above it will taste like it was made at Wendy's. It may be just salt, but there is some technique involved as well. The meat fat content Is probably 80/20 or 85/15.
So, I was at Wendy's yesterday. And the only thing to seem to have changed was how the menu was oriented. Previously a Number 1 was a single, a 2 a double, and a 3 was a triple. This is different now as "Daves" whatever is now all number 1 with the variations of patty count folded into it. The 2 is the Baconator, and 3 was something else. I got the mushroom melt burger thing though. So, I couldn't comment on if the Single, Double, or Triple tasted different.
I was there a month ago. It tasted standard. I have been at times where they over salted the burger, or the burger had fried Grease tassels like Five Guys or Freddy's has. The bun could play a big factor. Wendy's uses cheapo cheapo buns. We'd microwave in the bag for 15 seconds them to make them soft. Use Wonder bread, or Wal-mart buns if you make them at home. Other variations could be ketchup, and mustard brand. I think they were just Heinz before. Might have been Hunt's.
Edit: Apparently they changed from Heinz to Ventura 4 months ago. That's probably it. So tell em no ketchup and bring a bag of Wal-mart buns with you next time.