You should shoot to replace both of them. The egg only procs on heals, which means it's not procing on CD for you as shadow, AND has an abysmal proc rate. It's even terrible for healing, averaging only 5-7 procs over a 9 minute fight based on previous log analysis on our healers. As a DPS, I would imagine it's going to be much less. If you miss the proc with the long CD on Halo, you will have to wait even longer. Both of the dps trinkets from the heroic dungeons are better imo (flashfrozen resin globule and the vision of the predator). The Egg for the intellect alone will beat out the stopwatch, but I would get a dungeon trinket instead.