I am in the game right now, and another necro is chatting with me. He's a summoner, and is done with his build. He has loads of extra skill points left, and he said he wants to bump up his bone armor. He said he was going to put all his remaining points in bone armor. I asked another summoner, and he said the same thing.
Fact: If you want to bump up your bone armor, don't put points into it. Rather put points in bone wall or bone prison.
If you put points in bone armor, it increases the life of armor by 10 points per level, and also increases the mana cost for casting it. However, if you put points in bone wall or prison, they indirectly give +15 life to bone armor per level. Also, the cost of casting bone armor remains the same! Furthermore, bone wall and bone prison are very handy if you see yourself getting stuck, or just want to nag somebody else
I'll take the liberty of pasting the link from official battle.net site: Bone armor stats are here: http://classic.battle.net/diablo2exp...html#bonearmor
Hope this helps somebody.