Wobbly desk with IKEA tabletop and IKEA legs
As it appears the 'wobble' is between the metal leg, the metal bracket, and the bolts provided, I'd say this wobble is due to IKEA's ahem rather wide tolerance specifications. 

In other words, sometimes you just get wobble when it comes to IKEA products. :)

I'd suggest using something to solidify the connection between the leg and the plates. JB Weld would be a possible option. Mix it up and put a generous amount between the leg and bracket, then tighten up the bolts. Let it set up for about 24 hours and you should now have solid material between the two parts to shim the wobble away.