Ah well, I can understand the appeal that HR might have for you. Personally I get annoyed with players who think too much about the 'reality' of their stats,
Stats are there to help visualize characters as well as play the game (imaginative understanding of the stats can have them mean dramatically different things and there is more flexibility built in there than people think)
or who try to make every stat super.
People cheating on the die rolls in the old days... I remember them well... people not optimizing because all the attributes seem important in real life should absolutely not be compared to that!
D&D was designed with certain assumptions about stats, and if my players don't share those assumptions than I'm inclined to think that one or all of us should be playing a different game.
Way too dramatic of response.
D&D makes some really cool and interesting assumptions about attributes, heros will play to their best abilities (like winners do in real life) so being focused actually plays out as a good thing.
In real life specialists are also better at what they do and when operating in a team the team can succeed in grander ways (and realistically will sometimes fail in grander ways) A group of generalists neither fail as grandly or succeed as grandly as a group of specialists.
That lack of extreme failure...(might be something I think we can bring in).
One of my player's first PCs for a 4e game was a ranger with Con as his highest stat; he missed a lot, but I found it hard to feel bad.
Earlier games ( I skipped 3.x) were a bit overtly deadly and really felt like you were an apprentice without the kind of "fate" intervening which always happens for less skilled hero's in books and movies... you weren't heroic in any sense...Most characters even fighters could be downed in one attack no opportunities to flee. Boosting con and class choice was the only method for adjusting to it and the ranger was a high hit point 2d8 character so it sounds like your player both in archetype choice and attribute boosting was gaming for an earlier game and wanted to feel safe.
Players with preconceptions about how it will play have to learn the games distinctions... which is some of my players issues.. but with others it may just be philosophical.
If I were to use Keterys' HR, I think I'd institute it as a minimum attack bonus. Say, 3 + [3/4 level] + proficiency/misc bonuses. That way high stats still make you more accurate but non-optimizers are guaranteed a decent chance to hit.
Well that while somewhat targets... feels tooo patchy... and totally divorcing reliability of attacks from attributes is well dramatic enough to break too much if you do it wrong.
Having ways for "other attributes" to be useful can be a way to balance the problem of MAD because mad is no longer "a problem" ie overly unfocused character design will have its uses too. One example is making the lesser stat "sometimes" used in defense.
Alternate CA rule In place of +2 bonus.
Add a Disadvantaged Defense for each defense on the character sheet the value for Reflex / Fortitude / Wll is based on the lesser of the two stats.
For Heavy armor users if the adversary has combat advantage the attack targets reflex instead.
Note for monsters it might just be necessary to always pretend their armor is heavy and combat advantage lets you get around it. ( really stupid monsters become awfully hittable when you get CA if you dont)
shrug the main purpose is for pcs anyway ;-)