Yes, we need more PvE content in general. However I think PvE content can be challenging without 5star NPC's on alpha. What is the point of farming anywhere else if you can get the very best in complete safety? You can already do this with beacons.
There needs to be increased risk for high end PvE content like smarter AI that works together, reps eachother, specialized ewar bots etc. Increased risk does not necessarily have to be from PvP but it needs to at least match it in a way in order to keep game ballance. Something that challenges players in general.
And yes, the game needs more spawns. Let me breakdown current spawn ballance.
Alpha: A couple good 4star spawns for medium-high end players but not enough to support a larger population.
Beta: Some good 5star mech/hmech spawns here, probobly the most ballanced of all the islands
Gamma: Total crap, its currently not even worth your time to hunt down roaming NPCs here compared to beta spawns / beacons
Beacons: Ballanced just fine right now. The only form of NPC farming currently worth your time on gamma. Rewards increase as you can run them faster on beta and even faster than that on gamma with the right setup.
TLDR:
Add more level 4 alpha2 spawns
Make farming worth your time on gamma somehow
Add new exciting PvE content for all players