When a Necro has hastener speed, and his pet is attacked by a PvE mob, it does not break speed. As long as the pet does not do any damage the Necro and the pet both continue to have hastener speed. Have not tested in RvR yet.
Test:
Picked up Hastener speed at my house, ported to Fort Gwyntell, ran west until I could find some aggro. Pet was attacked, and hit, by a "First Run Assembly" multiple times and also by a "The forest watcher" multiple times. Neither the pet or I ever lost speed.
Test:
Picked up Hastener speed at my house, ported to Fort Gwyntell, ran west until I could find some aggro. Pet was attacked, and hit, by a "First Run Assembly" multiple times and also by a "The forest watcher" multiple times. Neither the pet or I ever lost speed.