Archer abilities are not "instant"

I have been leveling the Archer and have noticed that after casting a instant ability that sometimes you cant cast another ability instantly afterwards, for example, casting venemous bite then trying to cast Raging Strikes or Bloodletter which aren't on the global cooldown, they just simply dont cast, if the abilities are instant then they are instant, there shouldnt be a invisible delay that simply fails to cast another ability for any reason.

It is rather annoying because if you fail to notice that they just didnt work you could fail to get a life saving buff, self heal or last hit that finishes the mob.

Instant only means that there is no cast time and that it casts instantly. You still have a 2.5 seconds global cooldown after using that instant ability.

self buffs like Raging strikes and the special ability Bloodletter are not part of the global cooldown, they are separate so dont incur nor subject to the 2.5 global cooldown on main abilities

This is by design.

There exists Instant speed spells and abilities that do not belong to the GCD group. These spells and abilities, however, have a "cooldown animation" where abilities cannot be cast. This is by design both for balance, for system support and for aesthetics. The cooldown is around .3-.6 seconds, it takes some time to get used to.

by system support i mean that this game takes some liberties with position and timing requirements. The servers are global so these are used to mask the normal latency.

i still think its a bug, why would it be designed to have a invisible random length cooldown that doesnt give any indication as to when your able to use another ability making timing your abilites awkward.

and for a mechanic that other mmos allow for casting abilities in quick succession.

either add a cast bar for these instant abilties or make them truly instant, otherwise it plays like a bug and will frustrate players who are faster than it allows.

Time: anytime
Frequency: all the time
World name: Odin
Character name: Naksa Amberis
NPC name:
Monster name: any
Class/Level: 15 archer
Party or solo: solo
In-game time:
Area and coordinates:
Steps:
1. use venemous bite
2. straight away try and use bloodletter or raging strikes
3. nothing happens, ability doesn't work, no warning, no error
<*Add more steps if necessary>

Connection Specs
- Type of internet connection/provider: 10mb, virgin media
- Modem maker/model number

Model Number of the PlayStation 3 You Are Using
- Model Number: Slim model

I'm agreeing with Reader on this one. It seems that all skills that are off of the global cooldown are still ruled by animations. You cannot use an off-the-GCD skill until the animation of the skill previously used has finished. And any other skill used after an off-the-GCD must still wait for the animation of said skill to complete.
I agree with you Naks that this just feels wrong, as I am very accustomed to playing games where the animations for many skills can be clipped short to perform the next move. But, since it appears to be a universal issue for all classes I've played, I'm also leaning on the "it's intentional, not a bug" side of the fence, and will simply learn how to play through it.
Although, once they can find a way to keep the servers from flopping around like Magikarps, I'd love to see this discussion brought up again