so i tried telling another mage that the talisman was a waste, and boy was i wrong. I would HIGHLY suggest getting it. The extra mana is huge and i just pop the trinket every two minutes with AP. Currently talisman/Muradins is my combo. however right now, in icc25(lady deathwhisper especially) i highly highly highly recommend the talisman. I only bought the trinket right before a toc25 raid to test it out and right after the raid it was an easy decision to keep it.
Also nevermelting ice crystal actually dropped my dps by 600 when i used it with the the talisman(on test dummy self buffed when i was using dying curse as my other trinket) i would suggest disenchanting it or vendoring it.
to the persona sking about the charges...yes one set of missiles eats a charge so its a 3 min CD to be eaten up in 2.5 seconds(unhasted)