Okay first thing is first, know your hate multipliers that goes as such:

Savage Blade = 3.00 Enmity Multiplier
That is 100 potency non-comboed for 300 enmity or 200p for 600e (Actually 750e if you count the 150p from Fast Blade)

Rage of Halone = 5.00 Enmity Multiplier
That is 260p for 1300e

Shield Lob = 3.00 Enmity Multiplier
That is 120p for 360e

And Flash = (Weapon DMG*X)+(Strength*Y)+(Determination*Z) = Enmity
As you can see Flash is weapon/stat based and has no multiplier so you will always get more hate using your combos. So think of Flash not as your main hate tool but more as a 'placeholder' until you can use your more suitable hate tools.

Provoke has already been explained but one overlooked hate tool is Fight or Flight. If you are having trouble keeping hate, pop FoF. Your Shield Lob will become 160p/480e, Savage Blade 260p/780e, etc.

The second thing is, remember you don't have to use one combo on just one mob. So lets say you have your standard 3 mob pull. mA, mB, and mC.

You Shield Lob mA.@360e (if you they are far enough away you can sometimes get in a second one for more free hate.)
Then you use Fast Blade. mA@510 (870 if you managed to double up on SL)
Then you switch target and Savage Blade on mb. mB@600e
And you switch again to hit mC with Rage of Halone. mC@1300

You mix in flash generously and you've spread the hate around. I usually have my SL macroed to mark the target as #1 and Rage of Halone as #2. So even if you loose hate on the first target by the time that happens if the DD's are all doing their job it'll be near dead by the time it aggros the healer. So I go back to mB to since it has the lowest hate hit it with Fast > Savage. And then if I need to I'll swtich to mC and Rage. After that if mC is still standing I go in to MP recovery mode depending on how heavily I used flash and that's a wrap.

So in short.
Remember your hate values
Don't be shy about spreading your combos out over multiple mobs.
And remember to mark your targets/communicate with your party. Some times its as simply as saying "Hey DD's can you wait until the second time I use Flash to start attacking?" That can turn a nightmare of a party into a good one.