I agree with you, increasing the dmg (or just give us back the 3% dmg increase that was taken off us with last changes to Juggernaut class) and "fixing" the crushing blow would help a lot if not even solve our threat problems.
There are many ways, I just pointed out some alternatives. There are other options too and I dont care much on what way they go to fix it as long as they are caring about it.
Tank classes are different ... so I know that an Assassin tank for example can easy deal about 50% more dmg than a Juggernaut (bouth in full tank mode).
I really love my Juggernaut and I could not play an other tank. I will also go on playing and tanking with him regardless of the difficulties I find on my way.
For your example of the dreadguards, acually thats not really true as this is one of the easiest fighs agro wise as only the two on the sides can be tanked at the beginning and only the one in the middle gets killed first so only healing agro to keep up with and thats no problem (well, there are some bugs, more to that later).
Other fights like Denova Toth and Zorn or TfB the first one or Kepesh in there too requires a lot of tank swaps where I dont want to taunt to keep threat because of risking to not have it rdy when the mecanics require a swap.
Also there are some fights with agro dumps where you have to use taunt on and in the hectic of a fight I dont want to rsik having my taunt on cooldown here either.
Further on there are some serious agro bugs in the game at the moment that seriously needs to be fixed.
As an example the final boss in TfB hardmode in the second phase always agros our healers within the first 30 seconds of that fight even if we taunt he turns back as soon as the seconds of tauntlock runs out. And thats even with not healing at all (and there is no way a healer could pull agro from me normally on a single target and yes, in the third phase hes swaping agro on every hit but not on the second phase and after the 30 secs its stable again) ...
Or in Denova hardmode on Firebrand on Stormcaller I was tanking Stormcaller when a DPS of our Ops got agro from him ... this DPS was hitting Firebrand and for sure to far away from Stormcaller to hit him ...