is this normal when having phantom link and GA? (in General)

Here's a couple of rounds with Limping Dead:

Bela Legosi's Magic Missile hit Fat Monkey [559]
Spike Monkey absorbs damage [513]
Fat Monkey's Guardian Angel smote Bela Legosi (27)
Lon Chaney's Magic Missile hit Fat Monkey [490]
Spike Monkey absorbs damage [490]
Christopher Lee's Magic Missile hit Fat Monkey [975]
Spike Monkey absorbs damage [513]
Fat Monkey's Guardian Angel smote Christopher Lee (277)
Frank N. Stein's Magic Missile hit Fat Monkey [1230]
Spike Monkey absorbs damage [513]
Fat Monkey's Guardian Angel smote Frank N. Stein (430)

Damage inflected on fat monkey: 3254
Damage absorb by spike monkey: 2029
GA damage: 734

Bela Legosi's Magic Missile hit Fat Monkey [547]
Fat Monkey's Guardian Angel smote Bela Legosi (328)
Lon Chaney's Magic Missile hit Fat Monkey [461]
Fat Monkey's Guardian Angel smote Lon Chaney (276)
Christopher Lee's Magic Missile hit Fat Monkey [960]
Fat Monkey's Guardian Angel smote Christopher Lee (576)
Frank N. Stein's Magic Missile hit Fat Monkey [996]
Fat Monkey's Guardian Angel smote Frank N. Stein (597)

Damage inflect on fat monkey: 2964
GA damage: 1777

I did 3 fights with having phantom link and 3 without, the GA damage are about 1000 damage apart.

Why is the GA damage off so much between the 2?

If you use PL to absorb damage, only the remaining damage dealt to the original target, if any, will be retaliated by your GA.

Ah. I missed that line from the wiki. Thanks for clearing it up.