I have answered e-mail question about some useful fighting tips.
And they are proved useful and helped him finished the game.
So I decide to post them here too for anyone who has problem kicking some boss' butts.
"Important Fighting Tips"
1) Will Points
You should not burn out your Will to fight against all the enemies. Save it for boss fight.
(See my Will Characteristic Guide for more detail about stocking up Will for individual character)
Your main forces (may be Luke,Tiana,Frederick,..etc who is strong in your team) should have at least 120-130 Will points when fighting a boss. (At least enough to use his/her ultimate weapon)
2) Field Effect
Always remember that this game is about Elemental GEAR. And field effect really impact the outcome.
Never place Luke on the field with small downward red arrow (-10%) or big downward red arrow (-20%).
It DIRECTLY reduce Luke's Hit Rate, Attack Damage, Dodge Rate and Defense.
Keep Luke out of Snow area. Place him in the forest instead.
Same goes to the other characters of your team.
Tiana consider about green arrow.
Frederick NEVER need to consider about arrow color.
Harvein consider about yellow arrow.
3) Counter Abilities on Offense Attack
Always remember that Defender can always counter your attacks with his/her abilities in order to survive from your attacks.
Offensively trigger "Counter Abilities" and other abilities will ensure your attack's success.
Even if you see your hit rate at 95%, do not press "Engage" button.
Take a look at your enemy's abilities first.
Consider how much possibility that the enemy can counter your attack, then offensively counter those with your own abilities.
4) Burns Out Will for Defensive Counter Attack
The Defender always gain the upper hand with countering abilities.
When the enemies attack, he/she will not expected about our Full Abilities Counter.
So you will most likely be able to deal a LOT of damage all countering.
So many time in this game that I burn out my Will points in a Defensive Counter Attack to gain victory.
(But the best is to just damage him/her severely so that you can finish him/her with "Aptitude" turn on in your own next turn)
5) Choose your main forces
This game get a lot easier by focusing to build a FEW strong heroes in your team.
Easier than distributing EXP to every single people in your team.
When your main forces gain enough level, they will gain new level of abilities which will do great impact in their fighting performance.
And max out your main forces' GEAR stats, especially "Power"
For the easiest playing, I recommend Tiana as you 1st main forces. Luke as your 2nd. Ellion/Millia/Frederick/Tys as your 3rd.
6) Quicksave, Quickload Technic
This can be use for all boss fights or hard fights.
You shouldn't just quicksave anytime you want.
After about a number of fights, if the battle outcome is better than you expected or there are continuous successful in actions, then quicksave.
If your unit do some failure actions, don't save, don't load yet, try going on for a bunches of battles to consider about saving again.
You should save ONLY when your units have CHANCE to change the future.
Don't save when you don't even sure that there are survival chances within the next turn..
(If Tianerx is running out of HP-EN or her back are against the wall with no escape, don't save)
Don't save BEFORE the boss move in boss fight, but save AFTER the boss move.
This let you have the next whole turn to change the future if the boss make some expected moves.
God Bless You All. Be happy with the very nice game.