To find guide click on strategy forums, then find barbarian.

Actually the only nerfed part is the number of sockets.  You can still get
Cruel prefix (which is what matters after all).  I am sure about this, at
least up to today.

Bing

Concentrate increases your defense, attack and damage at skill level 20 by
290% 250% and 170% before synergies are factored in

Beserk increases attack and its damage (which is magic damage) at skill
level 20 by 385% and 435% before synergies are factored in.

So as it can be seen beserk will do more damage and is more likely to hit
and all its damage is magic damage, however the fact that it sets defense to
zero is a big drawback. Concentrate is weaker, is not interuptable does less
damage but boosts your defense.

I would prefer to use concentrate myself, but am put off by the fact that I
am finding it very slow going killing things, although I probably need a
better weapon.

As a side question is leap attack only possible when you aren't right next
to monster, ie can I leap attack monster that is attacking me hand to hand?
As leap attack seems very powerful.

The skill planner here is quite useful

http://www.d2items.com/skills.html

Depens for what you are building him for. IMO there is no better char on
Hell Baal MF runs then berserker barb. Reasons:
Warcry - incredible skill, Lister's pack is a piece of cake with this
Massive damage - best in the whole game, in 1.10 it's quite possible to
reach 1000% DMG (?!) which is why it is best for MSLE bosses, considering
95% have no resists to magic. It is a big difference wether you will get 1,
2, 3 or more MSLE emissions.
Natural resistance - free resists anyone?
Iron maide - forget about it, no danger

In my opinion defense still isn't that important (as it should be) - also
you have warcry for protection. I played those runes hundreds of times, died
once, lag.
Gear: in 1.10 still figuring it out; in 1.09 it was a 2-handed cruel
champion sword (because of practicly equal min/max dmg which makes it easy
to judge when you need to switch to ali-baba's), full resistances (F&L are
must), cannot be frozen mode (ravenfrost perhaps?). Now it is I think good
to go with maces, ribcracker ofcourse is the reason, but generally with
warcry and berserk - damage RULES, forget about speed as you will be killing
everything with 2 hits max.

Concentrate has it's advantages but it's more about defense, which I said -
is only important with no warcry builds but it comes with leech - you have
to decide what suits you better, higher dmg, no leech, or lower with
leech...

Hope I was of some help. Have fun!