I've heard that the Tear or whatever is currently broken. (You can spam spells and still gain mana without the cooldown or whatever)
Nah, they've always acted strangely.
Even in season 2 or even season 1, I've been able to use two spells before it would go on it's 'cooldown'. Now in season 3, it seems holding manamune and archangel's staff behaves oddly as well.
Casting a spell just puts both on cooldown, while only gaining 4 mana.
However, if you auto attack, only manamune goes on cooldown, allowing you to cast a spell afterwards to put both on the same cooldown. This gives you 8 mana. So much for unique passives.
singed + seraph's embrace.
Anyone with a lot of mana + Seraph's embrace = huge shield.