[Edit] Ignore this bit, I missed tyo's post about it being 33% reduction including speed bonuses from items.
As for the immunity, I'm on the fence untill I get a chance to really try and break the current mechanic, I can see where you're coming from but to me there just seems a real difference in between being stunlocked to death and facing an enemy demigod with spammy defence buffs.
Just to play devil's advocate in the mean time though:
A complete stunlock kill leaves you with no options once it starts, and given warp items/skills it's not easy to see that first one coming either. That feeling of futility was what was rather un-fun.
But facing a single demigod that's practically invulnerable due to short lived support buffs doesn't leave you with no options, if it's a big team game, there's more than enough of the opposing team to go out and harass the support demigods and still have 1 behind to chase the attacker away once his support dries up. None of the buffs make the demigod any more of a killer, just harder to kill so it's not too dangerous to ignore him and attack his support as a team. If it's a small team game there's not really than many buffs you can stack in a row, unless the attacker is oak or QoT herself.
As for those specific examples, shield is 6 secs with a 35 sec cooldown at max level, so they can't keep it up indefinitely. Still, 24 seconds is certainly a long time to leave someone whacking your defences so there's definitely a potential threat there. But whether the oaks can stop themselves being forced out of cast range of the rook is still dubious, if the rook goes back to defend them he's still only 1 more demigod worth of damage in a 5 demigod battle and he's no longer hammering your defences either so it's just a straight fight again.
The bramble has less of a threat, it's got a very short recast, yes, but it's going to go down fast under focus fire from towers and defenders. Re-applying it is going to eat mana very quickly and mean the QoT needs to get dangerously close much more often. I just don't think it could keep going long enough to be a threat.
I will say the rook's probably not the best choice as your demigod to buff, his high survivability doesn't mean much if you're successful in protecting him, damage spec'd UB or regulus would be better for a co-ordinated invulnerability tactic, both for higher damage and their ability to slow and chase demigods that try to pass them and reach the support.
The real test is to get a group together and try to abuse the crap out of them as they are. Now to find 5-10 willing players.
