For my money, they shouldn't be running into the 30d6 combat monsters during ordinary runs. Extraordinary runs, sure, but someone who's designed to mop the floor with people should mop the floor with people.
Sit down with your players - all your players. Find out what kind of game they want to play. Do they really want to play Combat Run? If so, go to town. If not, then give the 'Gotta Have It All At 6' player the gimlet eye, but let him build his character that way - with the clear understanding that he's going to spotlight only as frequently as everyone else.
Spotlight time is important. Does Mr. 3's and 2's have unique skills? What's that you say - he took locksmith at 2, which nobody else has? Guess what, the very next door is going to have a standard SuperHeavyDuty TrollProofTM manual-key-lock. If you want to up the pressure, force them to split the group, and put those locks in both places, and allow Mr. 3&2 to say sarcastically to GHIAA 6 "well, I guess you shoulda taken some other skills besides beat-his-ass-up, huh??"
A couple years ago, over at DragonCon, I played in a late-night game where several players (used 'gimmie' characters from the GM) said, "It's ShadowRUN - if you're not running away from something, you're not doing it right." This being the same guy who got into a bar brawl and nearly got his character greased. (I knew I should have killed him, but that's bad-mood-making in a pickup game.) The point here is that he figured 'combat combat' was the name of the game, when really it's 'spotlight spotlight'. Every player's character, at some point during every game, should get a chance to shine - and not always for the same thing, either. And after a few games where CombatBoy doesn't get a chance to slaughter the Hordes of Mordor, let him go to town - but then go back to letting everyone else do their thing.
Otherwise, remind everyone that they aren't individuals; they're a team, and need to support each other. If that involves having lesser outright skills but thinking ahead (as I would guess Mr. 2&3 does), then that's as good - or better - than just having lots of dice to throw. And you, as GM, should highlight that.