Pallymar posted a very insightful article on his blog about Mana Pool vs. Crit Rate and the reason Ulduar paladin T8 is so badly itemized.
It refers to this post on the Elitist Jerks forum in the The Holy Paladin Guide for WotLK.
Reading these numbers, paladins are not far, fully raid buffed and itemized in full T7.25, from reaching the point of being able to chain cast Holy Light without pause, just using Divine Plea and our other mana reducing talents.
At 30K mana (a number some paladins are nearly if not reaching, I'm at more than 25K myself and not at all fully itemized), 56% crit is enough to reach this "chain cast" cap.
As Pallymar notes, this is the obvious reason for the crit nerf of the Holy T8 for paladins. But it doesn't mean that, with 4 pieces T7.25 and all other items from Ulduar 25 we can not reach it (see my post on Ulduar Holy Paladin loot).
Let's take the 4 pieces Valorous T7 (without the crappy chestpiece):
57 int 55 crit Valorous Gloves (blue gem)
77 int 51 crit Valorous Headpiece (met gem, red gem)
77 int 55 crit Valorous Greaves (red gem, yellow gem)
57 int 51 crit Valorous Spaulders (red gem, yellow gem)
add to that the best Ulduar gear (that we know up to now)
(I use actuel best in slot for comparison in the () they are in italic letters is considered still best in slot)
92 int 76 crit Breastplate of the Devoted (Chestguard of Bitter Charms 67 77)
42 int 36 crit Horologist's Wristguards (Bracers of Liberation 43 41)
57 int 49 crit Girdle of Unyielding Trust (Girdle of Unity 57 43)
62 int 48 crit Greaves of the Rockmender (yellow gem) (Faithful Steel Sabatons 50 43)
43 int 41 crit Frozen Tear of Elune (Life-Bender's Locket 48 35 yellow gem)
37 int 39 crit Drape of the Spellweaver (Shroud of Liminosity 43 38)
108 int Pandora's Plea (Forethought Talisman 0)
87 crit Eye of the Broodmother (Sould of the Dead 95)
42 int 46 crit Pyrelight Circle (Signed of Manifested Pain 49 46)
42 int 36 crit Ring of the Faithful Servant (Seized Beauty 43 38)
now take the shield & sword from Kel'thuzad 25
49 int 46 crit Voice of Reason
50 int 37 crit The Turning Tide
add gems, yellow as +crit gems, red as + spell power gems and blue and half +crit
you add +4*16 +8 = 56 crit
total of 912 int and 843 crit (+145 int +10 crit)
1043.05 int from gear (15% bonus to int from talent)
18.14% crit from gear (45.91 crit rating for 1% crit at lvl 80)
7.92% crit from int (0.759% / int)
final with BoK and Divine Intellect
1147.36 int from gear (+183.4 int from Ulduar gear)
26.85% crit from gear (+1.61 crit from Ulduar gear)
As you can see from the analysis of the Ulduar loot, several items will be kept from the T7 Heroic raids .... we don't have all the loot from Ulduar, but a lot items are really badly itemized for us.
The only items you will change :
Chestplate, Waist, Boots and one Trinket ... for +183.4 int and +1.61 crit
(most of that comes from Pandora's Plea, our only real target in Ulduar)