Honestly, I've never had significant problems holding threat, but I've been keeping pace step for step with the dps I run with.
What I have noticed is that our threat scales faster than the damage output with improving gear. I've heard people complain about their threat and I've been spending a lot of time thinking about why I don't have that problem, and I've come up with a few things:
There are a LOT of options in talents and very little that are actually worthless for a tank. That being said, there are two angles that need to be appreciated. First, you want to balance survival and threat talents and appreciate that often times the talents don't do both. Second, DK talents are designed significantly around compounding bonuses, so to get the best threat out of your spec you want to play to a theme on your damage/threat building methods.
Common sense, I know, but the same basic edict applies to gear as to spec, your stats need to be balanced in terms of survival and threat. If your gear is stacked with nothing but stam, defense, dodge and parry, your threat will be weaker than if you have some pieces itemized with hit and expertise. Strength is always a value, but pretty much every single tanking piece has a healthy helping on it, for armor anyway. Having decent hit and expertise values ensure that more of your moves hit, flat out this is major value for threat. Interestingly, there is also a serious threat value from improving avoidance values. More dodge+parry will give you more Rune Strikes (to a point), and Rune Strike can become a VERY major damage/threat component. In the most recent patch (3.0.8) this is transitioned from huge damage (often top 3 on my damage) to being somewhat smaller damage and a lot more threat. So more positive threat feedback for DKs with improving survival from higher level gear.
3.) Hard Work
At the end of the day, any tank, and DKs up front, you have to work for your threat. Know your moves, know your priorities, and be paying attention to everything going on in the pull. If you are losing threat on a single target hate match, against equivalently geared dps, then the problem can only lie with your priorities and how you're making threat.
2 things I recognize about my gear that not every (or even not a lot) of DKs have: Bladed Armor, and the Sonic Booster. The latter doesn't help most folks since it's engineering only, but it has a pretty high uptime and 450 ap is a nice little buff. Bladed Armor, I can't sell enough. Every tank can and should have Toughness, and you will be tanking in Frost Presence, if you aren't doing one or the other of those, you got some 'splaining to do. Those two will give you serious armor values, now more than ever (off my own sheet I think I'm sitting at about 29k unbuffed). Bladed Armor is 1 AP/180 armor per point in the talent (5 fully talented). With my armor and 5/5, that is over 800 AP! AP flat out, increases the damage and thereby threat of every thing we do, most every move that doesn't scale on weapon damage (which is in turn a factor of AP), they scale of a % of our AP. The threat value is pretty amazing for a tank (and conveniently smaller for a dps, such is the smart design of the talent).
We don't need threat buffs, to be sure, though I think the particular scaling is a little rougher on new tanks than better geared tanks. I don't think a buff to Frost Presence is the way anymore, not that I'd turn one down. =)