If you're willing to wait until closer to 10th level for FB you can take Endurance and Steadfast Determination from PHB2 to switch Con for Wis for Will saves and re-roll Fort saves. Human Cloistered Cleric (UA) 1 / Fighter 2/ Barb 7 / Frenzy 10 is pretty much completely party safe and is totally unoptimized. There are a few builds using Complete Champion that have ridiculously low chances of party Frenzy (although I think the best builds use Savage Species' Cumbrous Will which might not be widely available.) Still, with PHB 2 you should be fine if you delay entry (plus you don't have to really choose between Barb and Frenzy, you get a decent amount of both.)
Another weird access to Frenzied Berserker is the Unearthed Arcana Druidic Avenger. You might be able to find some combo with Master of Many Forms from Complete Adventurer if you can use flaws. Something like Cloistered Cleric (UA) 1 / Druidic Avenger (UA) 7 / Master of Many Forms (CAdv) 2 / Frenzied Berserker 10.
Requires 2 flaws to get entry feats and Steadfast Determination, but it's nice for Cave Troll (Monster Manual 3) form with all it's extraordinary abilities thanks to 4th level Spell Compendium spell Enhance Wildhshape. Your con will be at least 27 if you have no items or spells for a +8 to Will, +4 effective from Rage (+4 con and +2 Will save) along with about a base 5 Will, so you might need to scrape up a +2 bonus from either boosted Con or Saves at 11th level to pretty much completely avoid threatening your party (which should be fairly easy as a Druid since Bear's Endurance alone will do it.) The whole Special Attacks: Dazing blow, improved grab, pounce, rake, rend, Special Qualities: Darkvision 90 ft., fast healing 8, low-light vision, scent, Str 29, Dex 13, Con 27, and +11 Natural Armor will be nice with your limited spell casting and future Frenzied Berserker goodness.
It's a shame it basically requires Flaws however.