The power only give 1 pt of armor plus another point per 10 over the threshold. I know it stacks with worn armor but still, I feel like it's underpowered. Another thing is, how stupid it is that when you spend full action instead of half action, you imbue your shield with…colour!?! dafuk. If at least it was something like: when you spend a full action instead of an half action, you gain your willpower bonus in armor instead of 1, but only until the beginning of your next turn.

That would make the power a little bit better IMO.

Am I the only one who thinks the power could use a little upgrade? Am I missing something?

I don't know if it's necessarily underpowerd. Rather, you have to be a very powerful psyker to get a grand effect from it, which makes sense to me. If your psyker is lower level then one point of armour can make a big difference. If your psyker has mastered Telekenesis then the PT is 12. Chances are your Psy Rating will be at least 5, and if you've invested in Willpower upgrades, Discipline Foci and Power Wells then likley you're starting at 11 or 12 before invocation. If you invoke and are starting at 17 or 18, and you throw five dice and get something around 30 then you're suddenly sporting a +4 bonus to your armor. If you're wearing Mesh armor then you've just doubled it's value and can sustain the power. I think it scales nicely with the character as is.

You're right, I can get powerful in those conditions, I still find it stupid that for a full action instead of half-action, it only gives color to to your shield, like it's supposed to be useful.

Its for the roleplaying fluff
Being powerful and looking cool while doing it

Sure the 'Telekinetic Shield' is a little underpowered , especially when compared with 'Flesh Like Iron' from Disciples of the Dark Gods.

OTH when you combine BOTH, and realize that they stack with other armour and your original Toughness, yeah that can get pretty difficult to beat. You should realize that first response is a bit tongue in cheek. If you play a Psyker with both abilities, you quickly go to the top of the GM's hit list, so be careful.