Does the Dinc need to be rooted in order to have Froyo 2.2 build that was recently released?
currently, yes. HTC is working on the OTA update but it won't be available for the incredible until later in the year - HTC says "by christmas". so right now, the only way to get it would be to root the phone.
Remember rooting can screw up your phone... and you won't have Sense unless someone released a Sense-ified 2.2 ROM I haven't heard about. Plus, I don't think you will get the 720p video recoding and wifi hotspot that is coming in a rumored OTA update from HTC before 2.2 hits the phone.