I think OH is probably no longer a perfect bellwether, since the Democrats can now afford to lose it narrowly (by less than 5% or so) while still winning nationally (remember that final 2016 pre-Election Day polls had Trump winning by 2-4% instead of 8-10%, so a significantly narrower Trump win in OH would likely have meant MI & PA staying D).
On the other hand, I don't think OH is a "lost cause" for the Democrats in the same way MO might be, since the counties which Trump flipped in 2016 (mostly in the north central & northeastern parts of the state) all had a Republican vote share of less than 60%, meaning that they (along with the state overall) can flip back to the Democrats if they win nationally by modest (Obama 2012-esque) margins or better.
