Let's nitpick first.
Frenzied Berserker requires 4 feats. A Half-Orc Barbarian won't be eligible for the PrC until 10th level since he won't have enough feats to meet the prerequisites until 9th level. At 14th level, the PC will have one additional feat.
He won't be able to get the Greater Frenzy ability until 17th level. So scratch the +10 to Str.
At 14th level, he will be able to get the 23 Str at 12th. Rage for a +4 and Frenzy for another +6. That does reach a 33 Str.
I can't find the ambiguous two feats that allow a -6 to hit for +18 to damage. Are you refering to the Improved Power Attack class feature that gives you a +3 for each -1 you take while power attacking with a two-handed weapon?
Barbarians and Frenzied Berserkers don't have access to Weapon Specialization.
Let's take a look at it now.
BAB = +14
Attack while in a Raging Frenzy (Can you Rage and Frenzy? Looks like it.)
+14 + 10 (str) = +24 With a +3 sword = +27
Damage = 1d10 +3 (magic) +20 (str) An average hit will do 28.5.
Now add in some Improved Power Attack at -6 and you get an attack bonus of +21 with damage scaling to 46.5 on an average hit.
A little lower than your estimates. Not too bad. While Frenzied and Improved Power Attacking, the PC will get a +21/+16/+11 with an additional +21 attack sequence during a Full Attack. Of course, the PC also takes a -4 to AC during this time. As an NPC, the Frenzied drawbacks won't come into play, but most parties won't want to risk the Frenzied Berserker attacking them when the opponent drops.
So the PC is good at melee combat at 14th level? Excellent. They are rather weak at several other things though. Still, I don't see anything wrong with the PC being good at their speciality.
By contrast, a 14th level halfling rogue doing the Weapon Finesse, Two weapon fighting chain is going to have a 23 Dex and will attack with a mere +10 +5 (Dex) +1 (size) = +14/+14/+9/+9 attack sequence and will do 1d4 +7d6 with each attack he hits with when flanking and using small (non-magical) shortswords. Rather than casting Cat's Grace, the Wizard/Sorceror will cast Greater Invisibility, thus making each attack by our halfling a sneak attack and giving a +2 to hit and ignoring the targets Dex mods. Give our halfling masterwork weapons as well and you change the attack sequence to +17/+17/+12/+12 and each hit will average 27 damage. Not as impressive as the Frenzied Berserker, but not bad either. Especially since the rogue has a multitude of other skills to use during non-combat times.