I'm not sure if you need a job offer. You can't work off-campus since you are on a study permit, but TA/RA has a valid NOC code, so it should be considered a job offer.. I am a TA and RA since Jan 2013. So I declared them as 2 years canadian work experience and as current work. But since TA and RA are not considered continuous and full-time I got no points for canadian work experience. Also, TA and RA do not need a work permit and do not have and LMIA so I got no points for the job offer.
I don't know though what happens to the phD students on EE - they have released absolutely no information on that. I waited until my 3rd year cause one of the requirements before EE was to have completed two years towards you phD.
If your points under EE are close to the last draw, I say go for it! In the worst case your application will be rejected and you will reapply at the 3rd year..
As I mentioned before, CIC (after an ITA is issued) asks for an Offer and a Letter of employment.. It's really hard, if not impossible, to get such letters from a university. What i'll do is provide the offer of admission (that has the fundings for all the years) as an offer of employment and a letter from Human resources stating that I am employed (until the end of this semester) as a TA and RA. I hope these will do.
As far as proving the past work experience a letter from HR stating the job description, the salaries, the time-periods and the hours is enough.. I hope!