I totally agree that items should have some trade-offs, and new loot should't always be better than previous stuff in every way, but the issue with T13 gear is that it was mostly created with the theme "give gear cool unique effects, and less stats", then the cool unique effects got mostly removed or severely nerfed and the stats never got looked at again. Players have been whining about this ever since the nerfs, but in a lot of cases it didn't matter because players could reach skill/stat caps even with some 'lacking' items.
The simple fact is, most of the T13 stuff that was changed needs to be looked at, and gain some raw stats to be in like with previous power gain from gear. There are a ton of item comparisons of a T11 loot and a T13 loot, and the T13 loot will have like 20 more hp, less stats, and similar focus/mods/etc. Any previous gain of two tiers would be more like 60hp, 40 total stats, better focus/mods/etc.
I know there is a worry about players getting too powerful, but some hp/mana, (over cap) stats, skill mods, etc aren't making anyone super powerful. The stuff that made players crazy powerful were channeling, 2min vah, crazy procs and clickies, etc. Nearly all of that stuff is gone now. Giving some high end gear a bit of hp/mana/stats won't come close to replacing that stuff, it will put things more where they should have been to begin with.