Bottom line, to answer the OP, IMHO, a portion of F2P is worth a try unless the decision has been made as SuperDud said to just let it fade.
I see few other viable strategies.
Vulkan? The only thing I can really see that buying is cross platform. It doesn't seem to me that performance is a problem for AH.
So, to Mac? LoL. Linux? I don't know that world. Is there a gamer culture on Linux? With numbers?
Console? Big money there but the current graphics would be insufficient I would think. Console players really expect AAA graphics.
If there is another more likely successful strategy, I can't guess what it is.
Maybe HT should just ... advertise! Yeah that's it. All you have to do is advertise. Why didn't anyone think of that? Maybe set up a table at air shows and hand out t-shirts and bumper stickers? Has anyone suggested that?
So what is the best strategy? If not limited F2P, what is the next best option?
For those against limited F2P, I'm all ears and interested. Honestly interested. School me.