Most likely a stop-gap/place holder until the Launch Day dust settles and they can address the issue. I believe the Hives were meant to be the place to go for good loot. Looking forward to what they have in store . Also, I hope TEQs are allowed in Hives for some awesome "Space Hulk" action!

I have a feeling it's a temporary "solution" to prevent people from possibly exploiting PvE somehow and getting a crap load of requisition and experience easily.

It's most likely this.

1000 exp for the cap that gives time, 500 for every other cap on that point imo

If they removed xp from any action but "Completion of a Stage" and made the xp reward raise the longer you got, then it would be much better imo.
The numbers are just to make an example of what I mean.

Stage 1: 150 xp
Stage 2: 250 xp + 350 xp (increase per wave)
Stage 3: 400 xp
Stage 4: 450 xp + 450 xp + 450 xp
Stage 5: Victory 1000 xp
Each Warrior slain should reward the group with another 500 xp.

Total: 4500 xp if both Warriors are slain.

Playing on Hard should reward you with 50 % extra xp, so the total would be 6750 xp (possibly still a bit to low, considering how hard it is).

before it was fixed at 1k I actually made around 10k exp per normal completion.
for teh time invested that seems to be fair when comparing to what some of us are making per match.

Id say 12k exp total for hardmode and 5k for normal. (or xcrate until user has all of em.)

When I played on Tuesday (i think) there was no cap and you'd earn 2 xp per kill but +30 for a streak kill so you'd end up with 3 or 4 thousand points by the second room.

yet another broken pile of crap

The problem with rewarding you for kills, is that doing so would reward to for kill hugging instead of actually trying to work together and win.
Who would willingly take the role of "flank defender" or something like that, if they knew they would get a far lower reward for the same amount of work as the Devastator who just fires away?

I think if they only counted the total tyranids killed collectively and awarded xp by the milestone to the whole group it could work out well; (ie: 25, 50, 75, 100, etc.) maybe give flat xp on room clears or something instead or for sticking close together or using teamwork (ie: small xp bonuses for killing suppressed enemies granted to both the killer and the suppressor).

but of course something like that could also easily be gamed if it was handled poorly but the pve should definitely focus more on rewarding cooperation and teamplay over individual kill counts and such.