Yeah, the non-heavy weapon jetbikes confused me too, I know some people like to take them as meat shields but it makes them unlikely to get to shoot for the whole game. Personally, I would prefer 3 cannons to 2 cannons and 2 catapults, given that any serious shooting at them is already likely to either wipe them out entirely or send them skittering off the board, which is quite likely given their leadership and fall back distance. Generally the best way to keep them alive is to jump out from cover, shoot something and then assault move back into cover, if your opponent can't see them then they don't need to be tanky.
I would concur on the point of the reapers as well, in my (limited) experience their long range coupled with their ability to move and shoot means they are rarely out of things to shoot at, and therefore any turns spent in a wave serpent are just turns spent not shooting, although in fairness, also not getting shot at.
I'm not sure about the Hemlock either, I have never used one personally, but I have used the crimson hunter, and I feel that the crimson hunter (which is cheaper than the hemlock) is too expensive and fragile to be used on its own without good anti-air and/or reserve shenanigans.
Apart from that I do like the list, you have good long range firepower from the jetbikes, reapers and tanks, and the hawks, spiders and fire dragons can cause serious pain for whatever they land next to. Farseer (I assume with jetbikes) can sit around and buff whatever needs buffing.