I did forget to mention the Exarch's ability to re-roll armour penetration, which helps a fair bit, but it is still a longshot.
In my opinion Spears just need a few tweaks to make them brutal:
#1) Lances should be AP2/AP3, with that extra AP on the charge, whereas star lance is AP2/AP2
#2) They need 2 base attacks, or some way to gain an extra attack, one attack each is just silly.
#3) Why did they lose hit & run? They had it stock last edition, and for purchase before that...
Would make more sense for the Exarch's current ability to become their "stock" aspect power instead of Aerobatic Grace, and for the new Exarch ability to be Hit & Run. Aerobatic Grace is kind of annoying considering they get a 3+ jink anyway.
In terms of sheer disruption power or tank glancing ability, especially for points, the cake goes to Hawks and even spiders. Last codex I tried several times to use Shining Spears, and really struggled.