The 990 Chipset is doing exactly what it is designed for, be built for the AM3+ which is a die-shrink, it will use less power to do the same job.
The reason for most 790 chip failures was due to a lackluster VRM used by most AIB's however those who used at least an 8+1, those boards have been trouble free for a long time. One of the Greatest 790FX board was the MSI K9A2 Plat V2 which had the most PCI-E Slots of any board for its time, four PCI-E x16 slots which with all for used ran at x8/x8/x8/x8. Folders use this board to this day in 24/7 enviroments powering GPU farms.
You are being unreasonable, the AM3+ is designed for AM3+ CPU's first, with compatibility for AM3's. Have you tried disableing two cores on your Thuban? It's looking like to me that the AM3+'s following AMD's specs may need considerably less power then the hungry Hexa AM3's as while using my 1100T as a quad core, I run into almost no Vdrop at all.
Yep and an temperature which is rocketing to the sky!
Actually using an air cooler (The Zalman 9900Max 135mm) I was able to keep my 1055T just below the TJ Max of 62C (Kept it at 61C) with an ambient temp of 29C. This was at the bios 1.6v which landed me at 1.505v under load. On top of that using both C1E, and AMD C&Q kept my idle voltage down to 1.3v when the CPU idled, the only time CPU-Z would report 1.6v with C1E and C&Q off, or during a power transition state when C1E and C&Q were both enabled.
Keep in mind it may simply be the fact that your 1055T was on the lower end of the BIN like mine was. As I told you my 1055T is a voltage HOG, needing to go over 1.4v just to get outside of 3.3ghz, while my 1100T is a very high BIN chip needing only 1.275v (1.22v on load on the UD5) to do 3.6ghz, 1.35v (1.28 load) for 3.8ghz, 1.4v (1.328 load) for 4ghz, then north of that to go higher.
The only thing I am wondering now, is are you setting the timing for your ram correctly, are you setting the multi's for you HT and NB down to accomidate for the higher FSB. I do not know these things, as you have not shown us what setting you are using.