since u understand this ,,, for my sentinel i used aim for 35% crit 75% surge now i understand crit is less usefull am i correct in my conculsion its now useless to go over 25% crit  and 70% -80% surge or am i looking at it all wrong ?

The chart mont posted is for the diminishing returns, so you can only use it to predict how much increase you will get from investing in a particular rating.
I dont think they changed the way damage is dealt, from what i have been able to dig up they calculate it as follows (from the forums)

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.

So if the two roll system is still active (and i havent found proof that it did) your crit/surge numbers should still be viable. So it is not useless to go over 25%   BUT...

They changed is the way your crit and surge rating "works", in the new system. To explain that i will have to go into the forumla's unfortunatly (again got them from the forums)

The most important formula is Skill=Base % + Asymptote % * Coefficient  This shows you that your skill will never go higher then Base +Asymptote.   The coefficient will go to 1 for ratings reaching infinite.

So if we for example take the contribution of crit rating to your critical hit. You will get   Crit chance= 5%+ 30*coefficient.  which will max out on 35%

You can test this by inserting a really high number for rating in the formula,  you will see that the formula will end up looking like 5+30*1

note they dont factor in skill bonusses etc, so it is possible to go above what the formulae predict

Critical Chance - Changed in 2.0  (only applicable for level 55)
Base Crit%: 5%
Crit Rating Contribution: 30% * (1 - (1- (0.01/0.3))^(Rating/55/0.9))
Primary (& Secondary where appropriate) Stat Contribution: 20% * (1 - (1- (0.01/0.2))^(Rating/55/5.5))

Surge - Changed in 2.0  (only applicable for level 55)
Base Surge%: 50%
Surge Rating: 30% * (1 - (1- (0.01/0.3))^(Rating/55/0.22))

disclaimer i tried to intrepet the formulas as good as possible, i cannot be held resposible for incorrect formulae nor for misintreptations. It is your responisbilty to check my predictions :P