I think the vesting schedule is back loaded because they give you a pretty large sign on bonus in the first two years.
Your total comp in year one would have been 112.6k which seems about right. The stock price doubled last year, so you would have been looking at at least 125k in year two.
Given the competition, I don't think the sign-on bonus is that large. It only barely makes up for the difference in salary that you can get from a competitor.
E.g you can easily pull $100k to $110k in base pay from similar companies out of school (think LinkedIn, Twitter, FB, Uber). Even well respected startups pay more than $90k (and that's not including any additional bonuses they will surly pay)
Your total comp in year one would have been 112.6k which seems about right. The stock price doubled last year, so you would have been looking at at least 125k in year two.