I respect your assessment of current state. I love Grieg's grit and pest factor, something the Sens are lacking, or at least it has yet to be demonstrated my many other than say Brady.
The issue I see with Grieg is his puck handling / play-making. It's just not there, at least not to where he should be slotted anywhere near the top 6. IMO, Grieg has been misplaced there for much of the season, and he is nowhere near ready for that. It remains to be seen if he can improve his play making, but way too many plays die on his stick. I have been a proponent of playing him no higher than bottom 6, to give him a chance to figure things out. Placing him in the top 6 against oppenent top defensive players effectively neuters him.
As for trading Grieg, I would not like to see him moved as I think that might be giving up on him too early. That said, it is fair to observe that a GM who has too much of a similar asset and little cap wiggle room may be forced to give up something good to get something good (needed).