1st Question is what is your Character Type and Stats (DEX mainly)
I´m assuming (from the current armor you are using) it´s a true Tank Armor question, since Barbarians and different builds require diferent things and also may have Armor type limitations, (Your question is HUGELY broad scoped btw
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Best Heavy Armors IMO:
* Tourney Armor (Desert): +4 Full Plate but has 2 max DEX, with Eldritch Ritual = +5...Full Plate.
* Dragon Plate (Regardless of color): See Definitive Static Thread for specifics but basically +6 Full Plate and ideal for Zero (shivers...) and Low DEX Tanks-Clerics, etc.
* Full Plate of Giants (Tempest Spine IIRC): +4 Full Plate and DR /5. (Add Eldritch for +1)
* Stonemeld Plate (VON VI): Same as above just looks way cooler and has 5x 1 min Camouflage...
* Plain Jane +5 MFP is probably the best all around Amor still. Why? MAX DEX 3; It´s not really Heavy Armor (Medium) so it can be used by Barbarians, and other classes; It also has a low ACP.
* Gleaming Adamantine Full Plate (I think thats the name): Ugly as sin, but interesting features +4 Full Plate, Adamantine (/3 DR), Command (+2 CHA skills) and Proof against Poison); also add Eldritch for another +1)
* The 2 Full Plates rewards from Silver Flame and Emerald Claw upgrades (Post Abbot) are nice but nothing major to them MAX DEX2 and SR 22, and such
And of course the Defender Full Plate from VOD. (But I have a mental block regarding this one....been outrolled by 3 times now on it) +5 Mithril Full Plate, +4 Protection, Heavy Fortification and +2 to hit)
Can´t remember anymore at this time, i´ll complete the list if I do.
Hope this helps.