Not really experienced with Malph, but as a (former) jungle main (always get supp now >>) I can tell you he's got potential to gank pre-6: you do need some other cc from the lane, but you can apply pressure by yourself even if they lack it (won't get a kill, but a good chunk of hp is pretty standard usually). I know this since I play mostly WW and Nocturne in jungle (and both can't do shit before they get to level 6, really), but if the lane is pushed enough and the laners have some good cc, even a WW can do a level 3 gank (probably won't get a kill, but will force a recall). That said: with weak team comps (or team comps with few hard cc) try to play heavy utility junglers like amumu, maokai, gragas, shaco: champs that can gank fine even before level 6 and have strong ganks through the whole game, with these comps you usually will not be able to win lane early, so the pressure is on the jungler to do something and if he can't gank, it's pretty much a lost game. On the other hand with strong early game champs or with comps with high cc you can freely pick a level 6 jungler, they usually have pretty awesome ganks that only need a small follow up to do the job and since your laners are supposedly strong, they can hold untill you're ready to go and can follow yo uwhen you go in. I've had people ask for ganks when I was at red, so before even minute 3, with WW so I know what you mean, sometimes people just want you to win the lane for them: don't gank those lanes, they will waste your time and will get you often killed.
Also with junglers like WW or Nocturne, especially if your mid laner is a mobile and bursty champ (like an assassin) you might want to focus ganking mid, since a fed, roaming mid laner can be quite scary and can gank when you're not (letting you get some deserved farm) or help your ganks, also since WW type junglers are quite weak against two or more opponents and top laners are hard to kill, so you will hardly snowball off of them, mid lane is the best choice to gank. If you have a strong aoe gank jungler (amumu post-6, gragas post-6, hecarim post-6, really any jungler with an aoe hard cc) try to focus on bot lane since you will easily get a double and a free dragon, which can be enough to win you the game if it's a fire/ocean drake and the adc took both kills (unless he was behind by a lot).
This aren't iron rules (I'm a former jungle main, I hardly play the role anymore so I'm just telling you what my conclusions are now that I finally understand the game better), they are just my tips: a strong early ganker (especially a diver) into a strong early team comp can snowball the game so hard the enemy will be behind by 2-3 levels at the end, while a level 6 ganker into a late-game team (if the team can hold untill you get to your powerspike) can controll the whole map alone, and I'm not joking: a WW type jungler, if left alone, can easily destroy the enemy jungler even if he's a bit ahead, securing objectives and preventing ganks all by himself and also gank lanes with a good chance of success if he's got nothing else to do.
Obviously this takes into account that your team is skilled enough to play at least at the same level of the enemy team, but you can't control how your teammates play so you have to focus only on yourself ^^.
P.s. sorry if my english is bad, it's not my main language and it's kinda late xD.