There has been talk that Lydia is broken as far as leveling with you. Her health is really low. Is there a fix for her or one in the making?

Use console commands to alter her stats, as well as level for now. Target her and use setav commands. I.E "setav sneak 100" will give her 100 Sneak.

This seems true, because as my character got up to around level 26, Lydia was in Full Steel Plate and getting her butt kicked
constantly.

She used to be my buffer and keep the mobs aggroed on her while "pew pewed" from a distance with my bow, now I see her
going down on one knee pretty quickly as all eyes turn towards me....

I gave her a full set of enchanted gear that alters Health and health regeneration. I made her essential with the console and she's only ever "Died" once when she got stuck on swinging spike wall trap. She kept getting hit, stagged, hit again and again until she "Died".. over and over and over again. I had to "push" her out using Unrelenting Force, lol.

My Lydia has 967 Health and so much health regen it's crazy, lol.

I had to set her essential because she got killed early on, I was taking on a group of Black Mages and one was a higher level and took her out with ice bolts.
This time around in my new game, I've left her in Dragonhold (DragonHelm?) wherever and am playing the game solo, because I got sick of her standing right in the middle
of doorways or triggering all the traps I happened to be standing in at the time

Yeah, I liked having her follow me around. The comments she makes on some of the areas is pretty cool, but she triggers so many traps and she alerts any enemies I'm trying to sneak up on. She's really annoying =(

Yea, I liked that aspect too, when she'd say in wonder "I've never seen anything like this (or something to that effect), but yea, she may have had flashing police lights and an air raid siren on her helmet as far as stealth went.

It also seems like her carry weight is a little low for a tank type.
ALSO she is 1h skilled but always equips whatever crappy 2h I give her to lug around as a mule.

Oddly enough on my game, I am level 35, I'm mostly a warrior. I wear heavy armor and wield a 2handed sword & bow. Lydia is a much, much better tank than I am. She wields her 1-handed sword & shield and beats the mana out of enemies. Sometimes when someone is too powerful for us it will kill her, but they usually kill me even easier, though I have better armor. I don't think she is putting all of her level-ups into health like some of you are (I know I am not) and I am certain that her strength is also controlled by the difficulty. She is an NPC, and becomes more powerful on higher difficulty settings. I generall play on Expert. (Started out on master, but the game got harder as I leveled).

I think the "problem" many of you are having is you're simply putting too much into your own health.

Target Lydia and type "getav health" and see how much health she has every level. That way you can see for sure if she's scaling. She is supposed to have a base level of 3 and match the PCs level according to the wiki.

getav health isn't going to tell you her level though... You have to check her level and see if it's scaling. I wouldn't assume that health increases for NPCs are linear.

Your companion's skill is based on your skill when you first meet them... or perhaps when you first load the city/area where they are located.

There is a console command to simply set the companions level to match your level.

open console, point at companion, type "disable" and then "enable".

Supposedly, this has no inventory effect. Just restats the companion to match your current level.

Read this on reddit this morning.. haven't tested yet.