I think claiming is working at intended.
In order to steal a claim, you have to take it from someone after completely suppressing them out of an area. The downside is that this allows people to very easily steal claims from small tribes with only 1 or 2 claims, who can't have people online all the time.
The upside is that it prevents massive groups from just dotting *everything* in sight. They can only control as much territory as they are physically able to respond to, which is a good thing. So while they might control an island with an iron fist, they need alliances in order to hold sectors and coops to go any further than that.
One way to address the bullying against small tribes is to institute a sort of backwards diminishing returns system. For example, stealing a claim from a faction with 50 claim flags may take only 25 minutes, but stealing a claim from a faction that only has 1 claim flag may take 10 hours to complete. (And obviously, moderate the human cheaty element of large groups just using an allianced second faction to protect their main base)