I'd say the
Magician Bard is at least Tier 2. He can take spells from any arcane caster's list like a built-in Samsaran Mystic Past Life, only you don't have to take all the spells from the same arcane class (and you can't just pick all high level spells). This also means he has access to Paragon Surge (along with Surge Imp. Eldritch Heritage Arcane tricks).
A
Sandman Bard can easily go up tiers by having allied casters intentionally fail saving rolls so the bard can borrow their spells. (Spells stolen by a Sandman are not "used up" for the original caster when the bard is finished with them.) For a bonus, the Sandman can make like a divine caster this way. Paladin or Ranger spells, anyone?
A regular Bard can also gain Paragon Surge and a few other spells through Improved Eldritch Heritage - Arcane.
There is also the Bard's traditional nuke: Glibness. I reckon Glibness's power as a campaign-wrecking ball is
rather underestimated. Granted, Glibness is only +20 in PF and Bluff can no longer do Suggestions, but +20 bluff on a bard is enough and you don't
need suggestion when you can make them believe everything you want them to believe anyway. All you need to do to go crazy with Glibness is have good charisma (Bard), high ranks in bluff (Again - Bard), and the willingness to activate Glibness and lie your way through everything. Even Zone of Truth effects get ruined by Glibness thanks to new PF text.
Also, are we sure that a Samsaran's Mystic Past Life creates a tier zero instead of an even higher tier 1?