This is a great skill and is highly effective when used at the right time
Level 40 tiger skills - Turbulent Seas: To tell the truth this skill isn't all that great. Though I do recommend investing a little bit into it as if you master the ability to lure in tiger form it can also be quite a hiero saver DFO Gold due to it is slowing effect.
Though I do not suggest upgrading this over frighten which should be maxed well before investing in this and is a much more effective skill as it is a 360 degree AOE and also reduces the mobs attack power.
Tigers Challenge: This is a great skill and is highly effective when used at the right time. I suggest trying to keep this skill at the highest possible level, though it's alright if you let it lag behind a level or two so long as you can effectively use ripping bite and frighten to hold aggro.
I highly suggest getting this skill to at least level 5 by the time you have reached level 70 as while luring in human form you will use this to keep the mobs aggro.
Also this will be one of your few useful skills in TW seeing as you can use this then perdition or vice versa.