WD Hitch or not?

The easy answer is....it depends. Assuming you don't pack the truck with heavy stuff, the tongue weight of the trailer by itself is probably not enough to make the truck sag. WD hitches also provide some level of sway control, so there's benefit there even if you don't need it to level the rig.

If you're towing without a WD hitch now and not having any issues, then there's your answer. If you are having issues, then there's your other answer....