Some reviewer said that the hashrate is like on the Frontier Edition(36mhs?) which is nowhere near 70-100 Mh/s
Highly doubtful. Workstation cards are never as good as gaming models for mining. Workstation cards use a different memory cache intended to fit large files. The Vega FE uses a HBC.
High-Bandwidth Cache Controller
The state of the art memory system on Radeon Vega Frontier Edition GPUs removes the capacity limitations of traditional GPU memory. Thanks to automatic, fine-grained memory movement controlled by the high-bandwidth cache controller, Radeon Vega Frontier Edition processors enable creators and designers to work with much larger, more detailed models and assets in real time.
https://pro.radeon.com/en-us/product/radeon-vega-frontier-edition/