Empathic bond has tons of weaknesses:
- PC, obviously
- CC -> less creatures, less healing
- very slow -> expensive card itself (you need at least two to make good use, so 2 cards and 10|8 life quanta) as well as you don't set up lots of creatures in the first few turns
- Shard of Gratitude serves cheaper, earlier healing (less, but don't depend on creatures)
- in a rush, Heal is better
In my opinion, EB is a but underpowered. In my PvP-experience, I've never seen anyone playing bonds. All in all, only high Arena decks with 2x draw and 3x mark can be sure to set this up fast enough.