Whats wrong with Tether?

They are all volatile coins, you just need to find one that is less volatile. That's quite difficult since all coins are affected by these dips. Investing long term is possibly the best way to go, don't panic sell when you see coinmarketcap go red. Thats the best time to invest and then hold.
I think eth is one of the stable currencies in altcoins and it had a great future too eth had nearly equal to bitcoin in future if it is possible eth will make a great group of investors like bitcoin .