My level 6 mage has the same hp as my recently died level 12 fully blown warrior. I'm talking about shield, armor, smithing and all defensive possible stats. A higher hp pool could certainly make those "oh sorry counter+crit, you're dead" bosses from lower levels...
There is no confirmation in there that it is a bug. afaik it is working exactly to spec. it may need balancing but there is no bug causing an issue. Every point of burliness and caddishness gives 1 hp. wizards get 3 per skill this way (1 from burliness 2 from caddishness. Warrior tree gets 2 (both from burliness). As an aside rogue skills also get 3 with the same breakdown as wizard skills. The only possible bug I can imagine is if the 2nd hp atrib was supposed to be stubbornness instead of caddishness, which both makes more sense and would put the warrior skills as having the most hp.
Not to mention that the master of arms skill that is supposed to make you "more stubborn" to have more hp, does, in fact, not give you said hp.
