Your attack power is calculated based on your currently wielded weapon - so if you’re a whirlwind barb you’re going to be using a 2handed slashing weapon, usually a sword. This means that your other 3 weapons do not matter DPS or attacks per second wise. They are entirely stat sticks.
Your attack power also doesn’t take into account things like ‘damage to vulnerable’ or ‘critical strike damage’ so for example, using the whirlwind barb again, if I unequip my 1h axe that has the following stats:
- damage to slowed
- critical strike damage
- damage to vulnerable
- damage to close enemies
- a socket with more critical strike damage
my attack power does not go down. This means that yes, attack power is unreliable. If you played Diablo 3 you’ll remember this being the case there too. You could equip a massive attack speed high end damage roll weapon and get crazy ‘sheet DPS’ into the millions, but in reality the weapon was terrible when compared to your slower, ‘worse’ weapon because of its affixes that could often do crazy things like give you a flat 800% damage increase to your main attack.
In my opinion your best bet would be to just follow a guide for your build over on MaxRoll, and if you want to make your own build - you can reverse engineer their thinking to see which stats would be best for your own build.