Since lax covered the easier way, here's the #waytoomuchfreetime way to address what you're looking for
I've set up a small set of click bars for each team that send macros/commands to WoW for each character. At first I just had it spam the same action to all characters at once , which makes sense with things like defensive procs for dungeon/raids, but maybe not so much for things like health pots/heals. More recently I've added modifiers to the click bars (like alt-click sends to all melee or all ranged), which helps a lot with the individual control and ability of the team. Handy as it's turned out to be, it took a lot of time to set up in any kind of meaningful, sensible manner, and remembering the right binds for the right toon/class/team/etc can be a bit of a cluster-f#%k under duress.
Click bars are great - the challenge is finding a practical way for YOU to use them. They can be amazingly versatile and useful, if you have an actual reason to use them. Starting easy with something i could have easily accomplished with a broadcasting key and building up and out from there made it a lot easier to organize and set up, so, maybe try setting up a simple action like character (or slot) specific bars that will trigger defensive procs to individual toons. You can find the wow media files (for icons etc) on github, or use your own. Since I have the artistic talent of a drunken 4 year old, i opted for the former to use in the click bar buttons.
I'd share some screenshots, but we're still awaiting the fix for 7.3 compatability (thanks for the hard work lax!!!), so I'll toss some pics up when that glorious moment arrives. Give me (or someone who might offer a better answer!) a shout if you got any questions