In patch 3.3 Blizzard is implementing a 20% dodge reduction via a spell that will be present in Icecrown Citadel's raid called Chill of the Throne. As Daelo points out, if your tank had 30% dodge, he now has 10%. They are doing this in order to negate the spike damage that's become prevalent in raids lately.
So while dodge will be nerfed, the ceiling on damage given to a tank will likely decrease. This will in turn, at least theoretically, make healing more about strategy (applying HoTs and planning heals) and less reactive (twitch response to apply the biggest heal at exactly the right time).
This is interesting to note as it's a move towards the Cataclysm way of tanking, as has been explained by Ghostcrawler: less avoidance on tanks, less spike damage, and thus requiring smaller heals.
Daelo's and Ghostcrawler's full statements after the break.
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