I would interpret "total dominance" to require something like an order of magnitude advantage; not "all things being equal you'll win," but rather, "you'll win, no matter what other factors come into play." Total dominance would mean to me that a TL14 commander who's a rock star with surprise is always going to lose against a TL15 commander of a similarly-sized force who babels and drools.
Total dominance in a single TL is borne out neither in analogous historical examples nor canon as I understand it.
As an analogy, we know that the numbers say that at TL7, a ground unit needs a 3:1 advantage to have a 50% chance of success in an attack. Thus if TL advantage gave "total dominance," then an infantry company at TL3 would have no chance of succeeding, ever, in assaulting a TL7 infantry company. Well we know that a TL7 infantry company in open combat with another TL7 company has routed the defender using a bayonet charge, a TL3 combination of weapons and tactics. Numbers said it it was very unlikely, but the combination of morale, desperation, fear and other psychological effects made it happen.
Lower TL forces have, throughout history, on the average fared very poorly against higher TL forces, but the progress has been neither uniform nor universally dispositive. The TL4 Swordfish attacking and crippling the TL5 Bismark with a lucky shot would probably have shot down if they had been the metallic, higher speed torpedo planes of TL5.
History is replete with such exceptions; indeed they are exceptions to the general rule that an incremental technological advantage will give a corresponding tactical advantage. There are times when technology advances, but some new technologies are not yet mature, or no new technologies essentially improve a given system. That is why our TL7 tanks mount TL4 machineguns, and why a TL4 rifleman has some advantages over a TL7 soldier with an M4 carbine in certain situations.
This is why I said it would give a 1 emplacement advantage but not "total dominance." (I don't know the numbers well enough, but I might even 2 emplacements, depending on the given factors involved.)