eating a system can pay for a few cruisers
or the maintenance time to recover from taking it
because cruisers are so expensive tyranids are always outnumbered and cant vring overwhelming force to any point

so you nerfed their forces with the point nerf
increased the cost as most tyranid attacks are semi suicidal
increased to recovery cost
increased the advantage the enemy had by having guns and outnumbering tyrandis who dont have guns
made their ships worse to increase the cost of what used to be semi suicidal attacks into definite suicidal attacks

and then did nothing to the resource per eaten system to compensate for all that

It's fine. You can grab even heavily fortified system with 3 fleets in it without firing a shot via forward actions that cost you 100 resource only. Takes time tho.

so its fine because you never fight a battle?