What i'm saying is not that it's UNCOUNTERABLE. It probally easily is but i'm not going to screw myself later by switching to ice at level 5 just to get stun. It's a waste of time. You need a SPECIFIC BUILD that isn't good against other demigods or creeps. This effectively kills off your effectiveness. Sure you give that oak lots of crap but you sacrifice being able to fight in other circumstances.
1st Dude you are so wrong here, lvl 2 of Rain of Ice will wipe creeps for breakfast( at the begining)
2d Try get Fire Ball from fire only + all Frost dmg abilities you can dish out HUGE burst dmg( TB really starts to shine from 10+ lvl)
Fire at high lvl isnt that great as Frost because of a lack of CC ( Stun, Snares, Interrupts are all in frost mode) + in fire mode you are actually HAVE TO close up on enemy to get your fire AoEs going, in ice you can back up easely(wand of speed FTW) do some research on damage of Ice combo + fire ball
3d if you got Pure Ice or Fire/Ice you`ll have no problem with Shield+HoL oak - stun or interupt him in his shield and you`ll dish out even more dps then pure fire.
Go to DemigodDb and do some calculation on dmg at lvl 15 for example, Reseacrh and dont take in considiration that Fire is more dps than Ice (Alive Ice do more dmg than Dead Fire, think about it)
PS sorry for english grammar.