Sounds to me like you're on a RP realm, or you're talking about random dungeons / battlegroups with people from a RP realm.
RP is short for "roleplaying", the act of playing your character as if it was yourself, using communications and actions that would respond to how that particular character's ehm... character is.
Also worth noting is that WoW is an MMORPG, out of which the "RP" part also means roleplaying.
When push comes to shove, all I really want to say is, if you're on a roleplaying realm and hate roleplayers, the best solution is to get a realm transfer to a normal or PvP realm (remember, RP-PvP is still RP!), or if it's in dungeons or battlegrounds, just live with it and/or turn off /s in your chat window while dungeoning. That's by far the best solution for all involved parties.
If I misunderstood your post and you actually meant people whispering you things like "Innervated you!" and "Focus Magic cast on you!" overly much, I'd personally just recommend making a macro with something along the lines of:
/r Please stop bothering me with whispers.
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and hitting that when you're whispered.
And if you're looking for an addon for automatically saying things based on what you do or what happens to you, SpeakinSpell is a good option indeed. I use it myself when roleplaying - sometimes it's fun to take the RP guild and do a raid completely in character, but it can be dangerous to stop what you're doing to type. :P