You can go Offense/Defense or Offense/Support with Tayrel.
Both ways are fine.
It just depends on whether or not you need more ACC on your Tayrel.
Players go Support tree when they are lacking ACC on Tayrel.
You want Tayrel to have 200 ACC for all the Stage 20 Dungeons + Nightmare Clan Boss.
You want Tayrel to have 250 ACC for Ultra Nightmare Clan Boss.
Some players can reach the above ACC amounts with out the Support Tree.
They go the Offense/Defense way.
Offense/Defense is actually how end-game players usually build CB masteries, so if you can hit the accuracy and speed needed for CB, why not.
Besides, you can switch out the masteries anyway (for free if you haven't done it once on a champ yet) if you really need the ones in Support Tree like Lore of Steel, Master Hexer, etc.