About Phantasy Star Portable 2 - equipping units?

[ZeroX4]

I'm LV 79,have A class armor,and use those extension abilities
HP Restore Rate - plus 10% of my max hp every 10 seconds
Photon Barrier - Damage amounting to less than 3% of your total HP is completely nullified.
Damage Resist - Cuts all damage received by 10%.
I play against Earth type monsters and my armor reduces 51% of the damage.

And with all that I still have to be careful when I play against LV55 monsters...what's wrong.

I can still clear solo some missions with LV 105 monsters but it takes a lot of time and careful attacking.
I don't have problems with monsters maybe 40 levels below mine(I have problems with some lv 40 monsters attacks...I can beat them easily but they still hit hard)

even for PS series that sound strange

i have better idea

why dont you buy some other armor for ur self in shop and check than what kind of dmg you get and maybe that will tell us the truth