halo time line

hey guys, just posting the halo time line and some problems i have with the series.
 
halo war= halo -1  (twenty year before the fall of reach)
 halo reach = halo 0 ( the fall of reach)
halo = halo 1   ( slightly after the fall)
halo 2 = halo 2  (after halo)
halo odst = halo 3  (between halo 2 and 3)
halo 3 = halo 4  ( final events thus far)
 
now for some problems. now, have you thought about the halo time line? have you noticed after halo 2 things started to downgrade. eg. the scorpion requiring 2 people instead of 1. i know 2 people will have the same potential but i can never find anyone to take shotgun. and now that things are going back in time things are becoming more advanced. wtf?  i know that they want new weapons in the new games but don't put them in the campaign. 
 
the final problem i have is flame grenades. you know why.