Part of the problem is her attack speed growth at max level is so low compared to the others. The reason Draven's attack speed buff is so low is because his base attack speed is so high.
Level 18 attack speed:
Tristana: 0.82328, MF: 0.991872, Graves: 0.933125, Draven: .990661.
Buffed, Tristana does come out ahead, but is much more reliant on it do wave clear, especially at early levels since it grows slowly at low levels.
Level 18 attack speed with buff:
Tristana: 1.54488, MF: 1.385472, Graves: 1.370625, Draven: 1.262261.
All of the other attack speed buffs you listed also grant a secondary bonus, bonus damage and grievous wounds on MF, a dash on graves, and a 60% speed boost on Draven. Furthermore, Both Graves and Draven have the ability to reduce the cooldown without a cap (stupid Explosive Charge), attacking non-structures with Graves by 1 seconds and simply catching an axe for a full refresh on Draven.
Honestly, if they reverted her attack speed growth and 2.5 and reverted Rapid Fire to 7 seconds of 90%, she would be in a better spot.