When thinking about strategies...
Two more thing come to my mind:

• after another post: some mention a time lag in the trends of the 'following' altcoins vs bitcoin... which could be helpful. I can see that as a theoretical possibility...but not how to use it exactly...For future research :-)
• maybe the logic itself but: don't judge a coins +/- trends on the trading pairs in your exchange (as the paired currency's trend can create a false impression) but on their absolute value on coinmarketcap...

[Edit: learning as I speak... I just saw JK mentioning in his videoblog there's a hughe risk of USDT collapsing... endorsing your last point :) !
https://steemit.com/cryptocurrency/@jeffreykirdeikis/the-great-crypto-correction-of-2018-what-does-the-future-have-in-store ]