The system doesn't assume that you Max it but it does assume there is an increase.
It's +2-3 in T1, +3-4 T2, +3-5 T3, and +4-5 T4.
This way the majority of the encounters you run into you will hit at least ~60% of the time.
Now if you never plan on playing in tier 3 or 4 then you could slap a...