Well, yeah. Miners can have a direct impact on prices so you should watch for threats. BCH is a threat on bitcoin as miners flee to it as profitability changes every so often. Also pools mining empty blocks promote bitcoin's transactions being expensive and thus limiting adoption. You should watch for sudden moves from miners.
But I will belivevthats important when they are making big trades in that particular coin. Aldo it won't be affecting on mass scale as long as they are being left from the mining and there are no miners left for confirming the transaction. In regard with value of that coin it will fluctuate more often with investment rather than the mining of that coin. The mining operation would be slow and it will take time to show the direct effect on your coin. Plus check the nature of your coin too because not all of them are mineable. ;-)
