General

@blargcat: nah dont reroll. when u use green mpe pot, it lets u bypass the soft cap (2) speed, and also allows any other +atk speed buff to bypass it as well.

e.g. whip (4) speed, booster brings u to (2) speed, mpe lets u bypass soft cap: brings u to (1) speed, then inner ability brings u to (0) speed
BUT if u didnt have mpe green it would be:
whip (4) speed, booster brings u to (2) speed, inner ability doesn't do anything becus it cant break the soft cap.

@blargcat: yes.
@stevenman76: if that is the case, the whole soft and hard cap has no meaning to the game. ofcourse nothing will go past hardcap since it's just "a dead end" but the soft cap will cease it's use if using a single cap pass pot bypasses all speed increases that was capped before the use of the pot. and if that is also the case, you're implying using the skills after the pot and before the pot will affect the attack speed differently?
E.g If you're at (2) and you used DSI first, then mpe pot. your speed will be (1)
but if you used the pot first, then DSI your speed will be (0)?
if you say that the order of the skills won't matter with the cap, that means you're saying that the mpe pot has "opened the door" of the soft cap not just "by passed" it.
If your logic is correct, if nexon were to release a pot/buff that will bypass hard cap, you will get you to what (-9) with a full pty of attack speed buffs?

TLDR: mpe is a single buff, cap is a "gate". mpe will jump over the "gate" while the other buffs can't.

@emoticongms: If MPE pot breaks the cap already, then anything else can go past the cap. EX: You're at (2) speed. You use a MPE pot and go to (1) speed. After that, DSI brings you to (0)

@emoticongms: So i should just roll over my +1 inner ability since it doesnt do anything?

DSI / IA / normal attack speed boost skills won't bypass soft speed cap (2)
MPE pot bypasses making it (1)

so Whip (4) - boost (2) / IA (1) = (2) [Soft cap] - MPE pot (1) = your final attack speed (1)

Source http://www.basilmarket.com/General-Attack-Speed-101-Wiki-303

@blargcat: It's because your inner ability brings your speed to 3 already and booster will bring it to 2 because of the cap, only with your green mpe pot you'll notice a -2 speed from your booster.

tldr : your inner ability is halving your booster's efficiency by halve without mpe pot

@chaosh: Ru sure Booster reduces it by 2? cause when i dont use a green pot snipe seems alot slower

According to Basil, Terminus Jaeger (whip) is Fast(4), indeed as fast as the Fafnir Risk Holder (claw). Booster reduces it by 2, MPE potion reduces by one and allow you to go bellow 2, and finally +1 attack speed IA is -1 (irony), so yeah, you reach hard cap.

With a slower whip, you would need DSI (Decent Speed Infusion), but that's besides the point here a guess.

TL;DR: Yes.

If your whip is the same attack speed as a fafnir claw - then yes.

Si maybe? No clue boo