I dont know why I have to keep stressing this to people.
@Magikarp: Weapon master is _useless_ past WM 4 or 5 unless you are planning to hybrid.
By level 30, WM 5 will get you around 150 WPF. Even if you have WM 8 you are only looking at about a 20 point difference (not much faster to allow you to outspam someone with only 20 points less). Much better to get the extra Power Strike so you can kill in 2 hits instead of having to hit someone 3 or more times.
Shield skill is also not as useful now that the forcefield is taken away, if a weapon is designed to break your shield or crushthrough, it will happen regardless. If it is a sword or a piercing weapon not designed to break your shield, it wont happen. That small HP bonus may make it survive a single hit more. Stick with ~5 shield skill.
To OP: As mentioned, swap IF for Athletics though, because Athletics is needed (most 2 handers will back away and spam you, you need to be fast enough to press up against them).
If you go higher STR, you will not only have the higher damage from PS but also more HP anyway, making IF somewhat moot. The goal I would say is when you feel comfortable being able to kill most non-tincans in 2 hits and surviving at least 2 hits yourself, then your strength is high enough.
Honestly my 27/12 with 4 Athletics, 4 Shield, 4 WM and 9 Power Strike does beautifully. I use a long weapon against 2 handers (sarranid cav or nordic champion), and a short weapon against other shielders (steel pick or broad axe).