That's a nice HBM clock you have there!

With Stak-XMR set intensity to 1008/904, worksize 4 or 8, strided index 2, mem chunk 8 or 16. Should get you over 1500H/s
https://www.upload.ee/image/8299205/memchunk16.PNG

Or use SRBminer, really easy to set up and only 0,85% dev fee. Dual threads and intensity 60 nets also 1500H/s
https://bitcointalk.org/index.php?topic=3167363.0

Weird thing with my Vega is that I have to restart the miner several times until the first hashrate reports are above 1500, then it stays like that...