What is the secret in killing the griffin in the taebris forest - am having trouble killng him even in easy mode+::

Here is some general advice for this battle and any others should you choose to continue...
1) Make sure the difficulty is set to easy
2) See what kind of elemental attacks, if any, the boss uses, and wear the corresponding accessories. The griffin uses lightning attacks so wear anti-lightning gear.
3) Try attacking with the element that is opposite of the element it attacks with. In this case, use water-based abilities.
4) Adapt to the strengths of the enemy with abilities that you have. If you notice the enemy hits for a lot of damage, try lowering its attack. If you hit for very little damage, lower its defense. In the case of the griffin, if it evades all of your physical attacks, lower its evade. Vellamik has an ability called "Hogtie" that will do the trick.
5) Always buff up your defense and agility near the start of the battle, especially if you have the abilities that hit every ally at the same time.
6) If you haven't already, use the "Fight Plan" item from the menu. Go to Items -> Key Items -> Fight Plan. Change the battles to "Wait." (This will make the biggest difference as far as challenge goes) You can change these settings any time you want between battles with the Fight Plan.