Having fewer mining pools means more centralization of ETC, which is a bad thing in the long term. Therefore, if you are an investor, it is better to think about trying to mine something else or sell your ETH as soon as possible.
It doesn't matter for ETC anyway.it's been a pretty fucked up chain anyway for one to worry about centralization 
The chain has even suffered 51% attacks more than a couple of times: https://neptunemutual.com/blog/ethereum-classic-51-attacks/
2miners.com and f2pool.com are suitable options and allow you to mine another ALT pair.
mikeywith has something to say about F2pool — https://bitcointalk.org/index.php?topic=5481246.msg63489044#msg63489044. You might want to think twice about it.