Apparently every hit has a chance to to be blocked/shielded then absorbed including criticals according to game data.
I would very much like to see this "data".
...I rarely get crit for the same damage normal attacks on elites are 300~400, when I am crit hit its around ~1.5 but sometimes it becomes 1100, 1800, can you explain how those aren't being shielded?
Let's pretend for a moment that the base value of our given attack is 200-400 dmg. Crits in TOR are based on a 1.5 modifier (which can be increased via Surge). That gives us a window of 300-600 dmg on a crit. It will be extremely rare for you to see the "same damage" from any string of crits. Anecdotal observation shouldn't be taken as imperial fact. I'm not saying that's what you're doing. I'm just saying that it shouldn't be done.
However, that isn't to say it's not impossible that a crit can be shielded; the lack of combat logs makes it impossible to know.
impossible for a crit to be shielded.
The following is a quote from Georg Zoeller. I have highlighted the important parts for the reader.
We use a two-roll system for determining combat results.
First is a hit roll, accuracy versus defense, and if the attacker misses then no damage occurs. If the attacker rolled poorly enough to miss even discounting the target's defense then a "Miss" result occurs. If he misses because of the defense then the result varies based on the attack type, the cover state of the target, and the target's equipped weapons. All the possible results - Dodge, Parry, Deflect, Resist, Cover - are mathematically the same, but they can trigger different effects and are visualized in different ways.
If the attacker hits, then a second roll is made with the crit chance of the attacker versus the shield chance of the target. If a Crit or a Shield occurs then the damage is adjusted up or down (based on Surge/Absorb), and then it goes through to the armor and damage resistance. A critical can never be shielded, and an attacker with a high enough crit chance can push the target's shield chance off the table. It shouldn't be possible to get your passive crit chance high enough to start pushing off the target's shield chance, but there are short-duration buffs that push these chances high enough to come into conflict.
On Diminishing Returns:
All of the percentage-based "ratings" on gear have diminishing returns. The design intent is that all tanks will want a mix of Shield, Absorb and Defense ratings, with the "perfect" ratios varied by spec and play style.
For those of you who are unaware of who Georg is, he is the Lead Combat Designer for SWTOR. He's the one responsible for combat design, balance and implementation. Unless Georg and his team completely redesigned the combat system for TOR between the close of the Beta forums and launch... the previous statement is still true. Feel free to contact Georg
directly if you want confirmation of the above statement.