Definitely worth it, and your MT isn't a very good one. Hit effects threat generation and taunt accuracy. If you're only putting out 3k tps, your dps can't go any higher than that, and their performance will suffer. If you're doing a taunt-game fight (Impaler, Thorim, etc.) and you need to spam taunts to have one land, you're eventually going to successfully taunt twice and hit diminishing returns.
In short: hitcap is VERY worth it, your MT is dumb.
Forget about the hit cap if your not having agro problems. Have some +hit trinkets and food with you for those fights where your taunt can't miss or swap in the hit taunt glyph (I hear you DK:s have one too).
I don't think you understand DK's or end-game content clearly enough to be giving tank advice on very important ideas like these.
1. If people were intended to swap in +hit trinkets for "those fights", why would the Impaler require 50k+ hp in hardmode to survive? Certainly we can't use +hit trinkets AND have 50k+ hp. I'd pay to see anybody tank the Impaler with two +hit trinkets (grim toll/50 badge phys DPS trinket?)
2. DK's need hit to maintain diseases and a clean rotation properly. If you're a Blood DK, hit helps you self-heal more effectively with Death Strike. Nothing sucks more than having your rotation perfect, your diseases half a second from running out, then missing a pestilence and having to re-apply diseases instead of getting an extra deathstrike.
3. All tanks should have their hit at least melee capped, so that even if 3k TPS is enough right now, their DPS will be able to go higher when they get better gear or better with their rotations. Your job as a tank is to put an acceptable level of threat out, not to put a dismal level of threat out and tell the DPS it's their fault when they pull aggro.
Answer: you should try to be at the hit cap, especially if you are doing progression content where you really need to be reliable to not miss a taunt or anything. However, statisically in terms of TPS, you are getting twice the return out of expertise that you do out of hit before you soft cap expertise. A dodge is equivalent to a miss, a parry is worse than a miss due to you encouraging the mobs to beat you up more. After the soft cap, you have a toss up between reduction of parry gib as the bonus from expertise, and hit giving additional taunt reliability when neither are capped. I usually go with hit at this point due to both diminishing returns and the fact that "reliable" is the name of the game for tanks, directly after "hard to kill".
Really for those of us in ubergear, having the hit and expertise caps at the same time is not difficult. For the rest of the world, it is the balancing act of choosing whether expertise or hit is going to be more needed in any given situation. Carry both +hit and +expertise food, use elixirs to the same effect, and you should be able to compensate for whatever you cannot find room for in gear during progression, on the fights that you need it for. Perfect doesn't happen during progression, that is why you are going through all that to get the gear right?
atm dk tanks are severely gimped on exp and hit gear our whole t9 has 0 hit or expertise and most off set gear from toc is low on hit so i went for capping exp for dodge and am running around 5.5% hit which hasent gimped me so far minus not having 4 piece t9