2th said:until you dont have both up or flash isnt up and an udyr, ww, olaf, nunu, amumu, rammus, malphite, xin, jarvan, etc come out of the jungle with red buff and rape you
Tear or Catalyst are dependent on the champ imo. I go tear quite a bit and honestly if I have more than 3 deaths at the end of the game it's a rare day. Seriously so long as you position yourself properly and don't play overly aggressive without good team support and/or map awareness tear is fine. Better in some cases since I honestly don't want catalyst/rod of the ages on some chars vs. certain team comps.
If it's a mana hungry caster, particularly one you want to be able to spam abilities with, tear > catalyst most of the time. If you're so out of position that you have to rely on the little health from catalyst frequently something isn't right.