if it doesnt affect the other abilities, then yea go ahead and use it. its a dps increase. BUT making that call of using it outside OOC procs is what differentiates experienced ferals from new ones. Takes a while to know when to refresh or not.
In the guide it dose say indeed to only use on OoC procs, However i must i've missed that when i was reading it throught this weekend.
Basically the more uptime the larger the DPS increase is however it will be a DPS lost if you nerf uptime of Rip! Aggixx had a simulation report (whice i can't find) What it says is the difference from not using Thrash only using on OoC procs and out of OoC procs aswell.
Using thrash with OoC is important because it has the Highest energy cost of any ability you will use, but also a Higher damage-per-energy than shred. I think It's been said that you should use Thrash any time the bleed has less than 6 seconds remaining and it will still be a better use of OoC than shred.
The main reason people caution thrash usage outside of OoC procs is that it does not provide a combo point combined with its high energy cost. So if your rip is going to fall off before you will generate 5 cp's it is better to use shred.
So yes, higher uptime on thrash is going to be a dps increase over spamming shred with extra energy/OoC, even when factoring in the extra FB's you would be able to use, But be careful not to neglect Rip/rake uptimes as those are much more important.
If I don't think I can squeeze in a Ferocious Bite then I Thrash instead. I tried going with more FBs last week and my DPS went down so I'll be going back to more Thrashes this week. I'll probably get more Crits and OOC's this week and wish I had gone with FB but that's RNG for you.