Prior to this weekends DMF I didn't even consider purchasing any trinkets for my guardian. But with prices shooting down on both the oxen card= looking at about 6 k (using some of my old cards) and around 12k for tigers deck. How good exactly are these for guardian? I use boomy and kitty for os, depending on what my guild needs.
Tiger deck is not that great for tanking though. It's okay, but there are better options.
From a purely tanking/survival perspective, the Tiger deck is likely not the first choice someone would go for. However, before people begin just writing it off, it does have some uses, generally in the DPS department.
For example, I specifically use two agi proc trinkets for heroic Gara'jal in conjunction with HotW + Wrath spam, since the damage increase is quite noticeable. Basically, any DPS check fight where my own personal survival isn't that threatened or a concern, I aim for trinkets that will boost my damage output. Maybe it's just me, but there haven't been many fights where my own survival seems to depend upon my trinkets, even on heroic.
Both trinkets could see use depending on what you have access to.
I began with the ox deck first weekend of being 90 and found it very useful to begin with. But it got replaced by Warlord's Figurine as soon as that dropped. The tiger's deck I picked up near the end of that week still sees a lot of use; either as above on heroic garaj, or any fight where dps is more important than health (Garalon).
You'll also consider using the Tiger's if you run challenge modes and need to really push the dps out.
Just an FYI as I learned the hard way this morning, you cannot have 2 different DMC equipped at the same time. Regardless of which deck you choose, you can only have (1) deck equipped which IMO is crappy. I never paid close enough attention to the cards to notice this. I assumed you could not equip (2) of the same but I never imagined I couldn't equip the agi and tanking Decks simultaneously.
IMO Not being someone with a ton of gold I will wait till they get closer to 10k on my server before even thinking about getting one and that is assuming my group has not downed Elegon yet and I still have 463 trinkets