I don't really know what he was reffering to but swaping items should trigger GCD for spells and you should not be able to cast spells right after equiping items (if the spell is affected by GCD ofc). That's a fact.
About the macro. I have simmilar to your macro and i have absolutely no problems with it, no GCDs breaks it. My macro is:
#showtooltip Spell Reflection
/equip Rod of the Sun King
/equip Merciless Gladiator's Shield Wall
/cast [stance:3] Defensive Stance
/cast [stance:1/2, equipped:shields] Spell Reflection
Just tried it in the game, I can normaly spam it and spell reflection buff puts instantly, not after GCD. I can even spam it during GCD after another ability and it still puts SR buff on me instantly. Maybe you have some addons that switch your items when you change stances?
edit:
Zap wrote:I encounter similar with my rogue, trying to switch daggers for shiv.
This is correct. Unlike Spell Reflection - Shiv triggers it's own GCD. This means you should not be able to use Shiv right after weapon switch (this part was bugged before). If you want to avoid 1 GCD - you can use hemo for example (or any ability that triggers GCD) and equip new weapon for shiv right after that spell. After GCD goes off - you can use Shiv and switch weapon back right after that.