I still think Yautja would have the advantage in a non face to face fight.
Both cloaked, thermal imaging visor would make the Elite still visible, while the Yautja would still be camouflaged to stratigize. This alone gives them advantage to use mines/disc/plasmacaster to distract and/or take down the Elite's energy shield for the kill. And if not for the energy shield, I'd say this fight (unless face to face) would be somewhat one-sided.
Also, the Elite's plasma weapons still have to be aimed, while a plasmacaster locks onto a target automatically.
You call Yautja weaponry "traditional", but it's only traditional for them. Far superior to us. And I don't really think Covenent weaponry is all that superior to theirs -just different. In fact, other than the energy sword, most of the Elite's arsenal isn't all that different from ours.
And perhaps the Yautja have kept their weapons "traditional" because they haven't really come across anything that can beat them (on a regular basis, that is).