Look, I know you mean well and wish to contribute here, and to a point, this is a speculative thread, and yes, you did correct your mistake. But at the end of the day, if you're posting here, you should have, at the very least, a solid grasp of what a 1-sentence tooltip says and means before posting about it - in your case, wrongly.
The conversation about the relevant merits of the various talents is fine, so I am going to leave your post there in case people wish to continue that discussion (though I will edit a remark into it as well). But please be more careful - this is the second time this week I've had to address one of your posts. If you wish to enjoy a long and fruitful posting career here, please be more attentive to detail, take a little time to familiarize yourself with the rules and some of the other posts around here, and see what kind of posts are generally infracted and which are left alone.
In order for rune of power to be better than invocation (for arcane mages at least) the mana regen it gives would have to be at least as good as the regen we currently enjoy from Mage armor. If the regen isn't as good, invocation will be my choice, due to endless burn phases without the need for evocations cooldown.
On a side note, i can see incanters shield as being much more situational, requiring either a high incoming damage fight, as discussed already, or an "I'm standing in the fire to regen mana." it strikes me as a more pvp talent, except if glyph of evocation still regens health. With evocation having no cooldown with invocation, it probably won't survive as a glyph.
Edit: for another thing, raid leaders may require us to spec rune of power for prolonged fights to help healers/other mana dps classes regen mana. I'm assuming rune of power works on anyone who stands in it.
Edit again: yeah on second reading of tooltip the word "your" makes me think I'm wrong about others benefitting from runes