Well, commentary from a warbandpleb and pvegrinder;
It's bit confusing. Guard is the main purpose of having a tank in party - to mitigate damage, and on the side add some extra dmg pressure and possible debuff arsenal or buffs, some CC - yet the main task is mitigating damage in guard range, which is about as vital as it gets when ensuring that melee can function in a game where hordes of people play ranged dps due to relative easy of ranged low risk pewpew vs high risk high reward meleetrain, where a vulnerable melee dps has to push while taking often quite severe ranged pressure.
Were SnB tanks underperforming? Hardly. They are mostly either for warband specs, or pve specs. Some SnB tanks were good, others like, say BG, or IB, just trash (class balance issues) - and they are still there at the bottom of the barrel compared to better SnB tank picks.
Were ranged dps underperforming? Doubting. Yet, as result of change, melee dps trying to push with Guard help,will now melt faster, so this is an indirect buff to ranged meta game, which is pretty typical for orvr campaign and especially keeps/forts. Not that scs either lack ranged players.
Then, were 2h tanks overperforming? Also doubting. You have limited the availability of some vital CC gaming from SnB specs, meaning you need 2h for best possible CC puntgaming. Taking 2h instead of SnB was a conscious risk, of losing HTL + block coverage, in favour of extra dps from larger weapon and variety of other buffs that are in many cases locked to 2hander specs (all good BG stuff basically + SM WoDS which about as career defining as WL Pounce).
You have already "nuked" some 2hander specs in past, namely all the known 2hander warband specs;
in memoriam of;
-2hander Chosen - loss of Crippling Strikes (30% dmg reduction was balanced - assuming your enemy has actually competent BW players each pumping out 12.000 damage per second which they are capable of; -30% dmg to that and they are pumping still 8.4k dps - not my fault majority of the BWs or Order warbands are incapable of getting good BW dps players to play competently together)
-2h Knight - crit aura nerf, again running one 2hander knight in WB was worth the +10% chance to be critted on enemies when KOTB ran a melee aura combined with tactic - this was changed to affect one of their AoE abilities which is on 10 sec cd, which basically was a death sentence to the previous warband spec as getting said debuff out only every 10 sec and possibly parried/blocked made it unviable. That on top of having a high risk tank melting always before other tanks, and then having their dps melt faster as well.
-2h BG build - again, despite having been playing Destro warbands for about 2 years or so - we have never included a 2h BG in our normal warband compositions, simply because you lose so much from not taking a BO or a Chosen with SnB + multiple utility loss, for a possible gain of +10 chance to be crit on enemies assuming perfectly landed Crimson Death. Their Guarded target would melt fast, and the tank would also melt faster than normal warband tanks. Too high risk, limited reward - TUP running 0 BGs since forever, and because of today's patch, well, we already buried the coffin of the BG class, but lets add one final nail to it?
Why this all is so confusing - is because no one has given a good properly thorough explanation as to why 2hander Guard needed nerfing. Due to this change in meta gameplay, it will have after-tremors on both viability of meleetrains itself and boosting the power of ranged gameplay as enemy melee Guard is now quite abruptly nerfhammered.
..static positioning for most spells + aoe los = doom.