You're not alone with being frustrated at the sloppy suspension. I have a 2011 with 91k miles and it handles like crap. I just replaced the springs and shocks/struts on all 4 wheels along with the sway bar bushings and stab link bars. That helped quite a bit, but it's still loose. Not sure if the next step is to replace the upper/lower control arms all around. Are there any other bushings I should be aware of that would affect ride quality?
I bolded issues I found so you're not dealing with a wall of text.
I just wrapped up a complete teardown/rebuild on my 2010 at 187k miles. I had a front end clunk and the truck didn't feel as tight as it once did so I replaced anything that had a ball joint or bushing.
Ball joints on the front LCAs were pretty loose. I had to cut off the LCAs as they were rusted in place. I'd previously replaced the UCAs and they were still in good shape.
Tie rods were in better shape than I expected -- I would have run the original outers if I hadn't already bought replacements. The
inner tie rod on one side was showing signs of wear and was more loose than ideal so they were both replaced.
Rear LCAs were still in good shape but I replaced them anyway since I'd already bought the parts. The lower rear shock mounting bolts were in terrible shape (rust like crazy) so they got replaced.
I pulled the rear knuckles and checked all the ball joints. Most were in good shape but the
rear upper control arms were crazy loose. I could freely spin the ball joint between my thumb and index finger on both sides. Definitely worth checking those for wear. They're easy to and cheap to replace.
Replacing your sway bar end links and bushings were a good call. Cheap and easy.
What shocks did you go with? I installed a set of Bilstein 5100s in the rear with my custom coils (900lb) and it rides nice. The Rancho quick lifts were leaking so anything new would have been an improvement there.
If you have any lift you'd likely benefit from a
front alignment kit to get the camber in spec.
It's always worth mentioning
tires. I run E rated tires at 50 psi. It's firm but the truck tows happily.
How are your wheel bearings? Even the slightest slop there gets amplified.