With the Debut of the Teddy Buckler I became concerned for the game's balance......
Stat-wise it is comparable to the Heater shield or the Power Mitt. The most noticeable difference is that the Teddy shield offers TWO status resists while the Heater Shield and Power Mitt only have ONE status resist.
http://wiki.spiralknights.com/Heater_Shield
http://wiki.spiralknights.com/Power_Mitt
http://wiki.spiralknights.com/Barbarous_Thorn_Shield
http://wiki.spiralknights.com/Teddy_Bear_Buckler
Probably the simplest solution is to give both the Heater and Power Mitt MAX stun resist. This would bring them up on par with the new shield in terms of stat numbers.
So..... I'm not done yet. Currently the Heater shield is super cheap to acquire, in order to make this shield worth that new status resist I would move the branch off of the alchemy path down to the 3 star level. This way the player has to invest in getting 3, 4, and 5 star recipes before reaping the full benefit.
On a side note this would knock the BTS down a bit since it sort of falls into the group since it shares identical stat values at the current Heater. All that needs to be done is add a Poison Resist to the shield. It already requires a very high investment (with CR, tokens, and Arcade runs), why not make the reward worth it? Even better it fits in more with the Snarby armor.
Teddy bear buckler more resembles a gorgomega, but switches defense values and gives up the great shield bash for no MSD.
Heater and power mitt can get some additions to powers, but if you want them to be unique you could go down the "new status combo!", however a better way to do it might be "give same status combos". What do I mean by this? I mean that Power Mitt could get the same resistances as a grey owlite shield (fire + shock), it simply now acts as more normal defense instead of elemental defense. Similarly, the heater shield could become the omegaward's alt shield, giving freeze and fire resistance in the same exchange way that the teddy shield does.
However, after doing this, I would recommend giving all tortoshields a slightly higher health value than other shields. Not as high as the omegashield, but higher than other 5* shields (or 3-4* while crafting up) in shield health. This will give tortoshields move blocking power and make them still have high usage in places where paid shields (teddy bear, power mitt, not exactly paid but heater shield) would be useful.
Barbarous Thorn Shield is fine where it is right now however, seeing as it is the only offensive shield we have right now at 5*. It trades status resist for an ability to hit harder.