Please explain how 4E "reduced this broken-ness"?
I'll take a stab.
Unified, non-combat conflict resolution. The Skill Challenge with its subjective, scene/narrative relevant DCs (rather than world relevant). More than anything, they did it by moving success or failure in the resolution of nonviolent conflicts to discrete scenes. With respect to its potency to move units in resolving conflicts, that, in and of itself, made a deployed skill achieve relative parity with a spell or ritual (or money spent, or healing surges sacrificed).
Of course, there are other component cogs that play into that and stand on their own. One of them you mentioned (Athletics):
- A broad (not quite open but extraordinarily broad) descriptor skill system that provides hefty packets of player fiat with each chosen skill.
- The Group Check as conflict resolution. Another discrete form of conflict resolution. The most widely used Group Checks are Athletics, Endurance, Perception, Stealth.
- A multiclass feat system that is usually always worth it to take one (and they deliver skills).
- A Ritual system open to everybody who wants to invest.
- Amazing Skill Powers that are available to anyone who wants to invest.
- Heroes of the Feywild made Cantrips (including the extremely powerful "sub Arcana for < >" line) available to everyone with a few feats invested.
As for the Fighter himself goes:
- Athletics is an amazing skill with probably unparalleled bang for buck. You could make a case for it actually being the most widely applicable skill in the game. Conflict for conflict, it might be more "deployable" than any other skill in the fiction-first facilitation of a successful scene. Its rarely a reach, with respect to the fictional positioning, to use it, and the Fighter has ability in Athletics in spades. Further, there are some great skill powers (I'm looking at you Mighty Sprint) that are awesome in both combat and noncombat. It also works as your Escape Grab ability. It is one of the few skills regularly used in Group Checks (of which the Fighter comes near to auto-passing, thus immensely helping the group).
- Endurance is underrated. Its much more applicable than several other skills in a number of fantasy tropes as conflict resolution. Fighter again serves as anchor for the Endurance Group check.
Third skill for the Fighter is any number of very good skills. All that said, I would still give every class in 4e four skills. I suspect they went with the LOLFIGHTERYOUONLY3 for silly (and obviously incoherent given the ruleset) legacy purposes. Inexplicable. Regardeless, even with those 3 skills they do just fine in my experience, and I've GMed wizards with uber powerful daily utilities, rituals, and "sub Arcana for < >" cantrips. Those wizards are serious business, to be sure. But the two Fighters I've GMed have been no slouches. I'm currently GMing a single player PBP
here and the player of this Fighter is doing fantastically in noncombat conflict resolution (Exploration and Social). Manning the ship by herself. And she's cleaning up combat. This is someone who has played a Druid from 1-30 so she's familiar with noncombat potency. She's quite pleased with how things have progressed with this Fighter.
The biggest problem is the one at the top of my post. Conflict Resolution versus Task Resolution. Mundanes with a more narrow skill system, with less broad functionality in class overall, with objective DCs (that follow the world of process sim rather than following the narrative relevance of the scene) flat out cannot compete with the utility of a broad descriptor, win by fiat, spellcasting system underwritten by an OMGBUTMAGIC gaming culture (which is assimilated in its GMing ethos). It just can't. More than anything, I knew that model at the core of noncombat conflict resolution for 5e was its death knell for me ever running it.