That's not really all for 140 pts.
1) You get 1D3 CCP - Pretty reasonable
2) Every caster gets +1 to cast if within 12" - Really good all around, especially if you have multiple casters like Skink Starpriest etc.
3) Every caster gets 6" added range to their spells if within 12" (except Endless Spells) - Extremely good. This coupled with Balewind gives Kroak a 22" threat range with Celestial Deliverance instead of his base 10" range. It is pretty big and noticable difference on other casters too.
4) Every model wholly within 12" gets a 6+ ward save - It is pretty alright as it gives some protection against MWs, something none of our models have.
Every bonus is really good and you dont even have to roll a dice - It is just a passive buff aura as long as the Astrolith is alive. It is a must-include for me.