Just got this spell and tested it and here is what i found.
Does 100 damage to target.
The effect lasts 60 seconds and increases you and your groups (haven't actualy tested in group but recourse should be the same for group members) attack by 135 and slowly diminishes to 110 attack or so by the end of the 60 second.
Recast time is 72 seconds so this leaves you with 12 seconds of no attack boost which is kindof a bummer but overall it is a nice spell.