Other than the Marauder's Bloodthirst (15% increased damage and healing for our group for 15 seconds, on a 5 minute cooldown), what "big offensive cooldowns" does the game have which you feel like the Sniper should also get?
Snipers have 2 offensive cooldowns:
Target Acquired (10 seconds) ~2min or 1min 45s can't remember. Increases armor penetration for 10 seconds. The second one is Laze Target (1 min cd), makes your next Snipe a critical hit (4000 or 4500).
As for your question what "big offensive cooldown", that's not for me to answer but BW, hence the PVP question above.
I think people are putting offensive and defensive cooldowns side by side and see it as one: namely on the category of "cooldown abilities." (Theorycrafting only) If we establish defensive and offensive cooldowns as one, then many snipers would agree that (in PvP), the class does not really have any strong "cooldown" abilities that they can use as an "oh sh~" button. Cooldown abilities such as Saber Reflect, Endure Pain, Cloak of Pain, Undying Rage, Force Camo, Sorc god bubble, Vanish (sin/op), Shroud come to mind.
Hmm actually... we do have Evasion and Hunker Down. Evasion can save your life. Hunker down is good cc immunity but you have to stay stationary. When i see a sniper use hunker down, i just swap target or LoS him to force him to move. lol.