As has been said, it would change nothing about a fighters tier, it would just knock all other melee down a tier maybe.

That aside, I think the Tier system is really impractical because it makes a lot of assumptions about campaigns. in most campaigns i've played in, Fighters and barbarians actually tend to hog the glory with casters more on the periphery. Most of the gameplay is combat, and the melee really shine in the combat. A caster can occaisonally end a fight before it even starts, but then we just go onto the next fight, where most of the actual gameplay revolves around the fighters/barbs/etc. Sometimes the party needs to get from point A to point B, and the wizard gets to be the one to cast the teleport spell to make it happen, but it doesn't feel like the wizard is suddenly hogging the spotlight and making everyone else obsolete.

Now I understand that there are shennanigans that casters can engage in, esp in high Op campaigns where they can totally sideline the melee and make them irrelivent. I've yet to actually play in such a campaign.