I first took GMAT in November 2016 and I cancelled the results as it was only 590, but thanks to enhanced score report I know exactly how I performed, for the purposes of this meeting let me concentrate on IR (although, when I sat for test for the second time, I did actually worse on Quant too inspite of preparation, but that it is different story, may be..)
- IR score 6 (and given max score of 8 - it is 75% of max score)
What is interesting I did not do any preparation for IR except for doing a practice review test...Also, I did not have time to complete all 12 questions, I think I just finished 10 questions...

When I took exam in Jan 2017 I improved my GMAT score solely because of Verbal section and did actually worse on Quant and IR
- IR score 5 (and given max score of 8 - it is 63% of max score).
I completed 12 out of 12 questions. I practiced the tests a couple of times (plus had previous experience with actual test, it is interesting that it helped me answer all questions, but my performance deteriorated a bit, which may be just a play of luck.

In November 2017 I started preparation for Executive Assessment (also administered by GMAC) - I acquired OfficialEApreparation package with 100 questions (1 question got somehow lost- I completed all questions but it showed only 99, I have not idea, where the last one went and may be, it was the reason for my mediocre result ) and additional IR questions pack of 40 questions. I resolved them all with average score of 75% but I could not complete in time, so score is a bit misleading. I also put notes on difficult questions and tried them again....

When I took the actual EA exam the score for IR (and this one counts to the total score, unlike GMAT) was just 10 out of 20 or 50%!
I was able to complete about 10 of 12 question...

I consider this result as amazingly low, given extensive IR preparation... Really, I scored 75% without any preparation on GMAT, 63% at second sitting and then after preparation I had only 50%!
Could it be that IR part of GMAT or (EA) became more complex? Or it just tells me that IR preparation only makes things worse?

But my story was not over yet, as I decided to improve my EA grade and registered at the exam again I took in less then 1 month time for EA again. I did not do any preparation for IR and verbal part and just focused on quant.
I failed to improve my EA score - just wasted 350 USD of registration fee and my chance to improve it for lifetime well, current rules provide that you take EA only twice in your life! It is a pity really, I hope that they change it one day....
With regard to IR - I improved it by 1 point (making 55% of max score), but I did worse by 2 points on IR and 1 point on quant (even although I got just the opposite impression before hitting the end of test button

My personal takeaway thoughts:
- IR skills can not be mastered in short term or even medium term, probably you accumulate it over time or it is just dependent upon your cognitive abilities in general... you should be just aware of question types and I would rather suggest that you have good rest before the exams and manage your time wisely. .
- Retaking EA shortly may be not the best tactic....
- I concur that on IR it may be a better tactic to focus on resolving 10 questions rather than trying to do all 12, if you're under time pressure of course..