Do you sleep on your left side? I've heard that can account for hair growing faster on one side. Anyway, hair doesn't grow evenly. My fringe and front hair grows slower than the rest, and I suspect this is why the thinning is so much worse at the front than at the back for me. Others have experienced "racers" at the back or elsewhere. I remember one member said her hair naturally grew in a M shape.
I don't think there is any reason to cut more off, despite what your hairdresser said. You asked for 3-4" which is more than the 2" difference, so it just meant that more was cut from one side than the other.
However, if you're experiencing increased splits, you might want to first of all see if you can ascertain why that is happening and change up your hair care routine. You might also consider small trims more often - say 1-2" instead of 3-4". That might help remove splits before the travel further up the shaft and also help minimise that difference in length. Just a suggestion.
Hair Journey Began June 2006 ...
Hair Type: 2a/M/ii
Natural Colour: Mid-Dark brown with natural red and silver highlights (more silver than red nowadays); fringe/bangs (which I am always in the process of growing some out).
Starting length: 25"/62.5cm (BSL)
Initial Goal length: 36" (Tailbone)
Setback: Major shed in 2010 when at 38" while dreaming of classic
New Goal: Healthy hair that I'm happy with! (Preferably tailbone with thick hemline.)
Estimated Date: Mid 2017 for tailbone and then maintenance/beautification programme begins.
C = condition the length; W = wash the scalp using diluted organic shampoo or shampoo bars; A = acidic rinse, either ACV or citric acid; Frequency = once a week. In-between times, scalp washes as required.
Favourite Products: locally bought shampoo bars; A'kin shampoo; cone-free conditioners; avocado, olive, almond and coconut oils.
Other: Regular micro-trims; light oiling on dry hair a few times a week; BBB; wooden comb; Mason Pearson comb; hair sticks, Flexi-8's, Ficcare, and other hair friendly toys.
Latest Experiment: Washing with rye flour shampoo
'Your beauty should not come from outward adornment, such as braided hair and the wearing of gold jewelry and fine clothes. Instead, it should be that of your inner self, the unfailing beauty of a gentle and quiet spirit, which is of great worth in God's sight.' 1 Peter 3:3-4
My Author Website
On Eagles' Wings (My Blog)
My Method for Scalp Washes