I like the 245 helm more, but while you are grinding frosties for your T10 helm, try to get the t9 helm, and see if you can get into a 25-man ToC; if you get the trophy that upgrades the T9, the upgraded t9 will probably be better than the 245. Good luck!
You do NOT need the t9 helm to get the t9.2 helm, and EXP is MORE important than hit for a dk tank because rune strike does not miss. However...all that said...from looking at your armory you need the hit...a lot. Despite 50% of our threat coming frome rune strike, it is important for the other 50% that heart strikes and death strikes are landing, and you can not afford to have your diseaes miss or your threat will be non existant, then the hunter (since a hunter is my other 80) will pull aggro despire misdirecting, feign death, then pull aggro again and die while you are waiting for your runes to come off cd. So take the helm with the hit and even consider putting a stam/hit gem in it. Another thing to remember is for death knights even raiding ICC dodge is a THREAT stat as well as a survival stat (same for parry, but my dodge is always higher and on use trinkets are usually an amount of dodge on use) more dodge=more rune strikes. The ICC dodge nerf does NOT mean that dodge is not useful, the raid is designed with the 20% less dodge in mind and I still see myself doing pretty much the same amount of dodging as before. Again that being said...dodge/stam gems>pure dodge gems every time for me. Also farm reg toc 5 for the black heart, that armor proc is amazing until you can get the toc 25 or the frost badge stam trinket. Also glyph on indomitablity is a great trinket for ICC and is purchasable with triumph badges.
So like I said before I went on my rant...get the hit helm. Don't forget you can eat rhinolicous worm steak for some extra expertise.