Yes the Frenzy builds up, so if you have 10 in Frenzy, you actually have to hit 10 times before the max is build up. Then you can use another attack, double swing or concentration or Berzerk, and the game adds the Frenzy bonus as long as you are hasted.
So unless you plan to hit a mob 20 times, or think you can keep the frenzy going, I would take less in Frenzy, maybe 10 points, and then fill the attacks I would use the Frenzy bonus with.
Whirlwind doesn’t work well with Frenzy, the speed makes you fly through and not hit much. But Concentration and more damage more dangerous Berzerk surely does work. Concentration is uninteruptable and a “safe attack” when you have no shield, and Berzerk is a risky attack that lowers your defense, and you will take damage 
Battle Cry is a one point wonder, especially if you are going bezerk. It is not seen so often, because it overrides for example necro curses, and people prefer necro curses. But playing solo it is very effective. A bezerk build should use both that and shout, 1 point in each. A very high defense armor is also useful, as you are basically tanking mobs without a shield, consider the “Stone” runeword (Style points for using Balrog Skin or Wire Fleece). Or the unique Mesh Armor (Upgraded) with damage reduction, and the unique Vampire Gaze. An upgraded Skullders can work for MF too.
Crushing blow is a given % health pr attack (You can see it when the boss monsters health takes a jump), so the more you attack the more crushing blows. So your fast attacks makes this very strong. Craft Blood Gloves, and be on the lookout for Crushing Blow.
As for all melee, the weapon makes or breaks the build. The top end uniques will work. For runewords, I would point to Kingslayer, for a good endgame-start sword or axe, that can be build with Runes you can get from Hellforge quest. And even if you are unlucky, these runes will probably be tradeable as people actually get them from the quest.
I set up my skills on qwer, and asdf, and switch between skills on right mouse that way.
I would have either Frenzy on left mouse, and then conc or berzerk on right mouse and not use doubleswing. Or have doubleswing on left mouse and Frenzy as one of the right mouse skills.
It’s perhaps biggest barb damage dealer build, but not using whirl means you can get stuck in mobs (you can always take 1 point), but you can always jump out. You can also use the speed to MF run to a target, and as an aside, grabbing stuff in 8 player Diabloruns is pretty effective with your speed.
All this advice cause the servers are down