Tanks and assassins have two different playstyles and overall purposes in the game. When the masses start subbing in stealthers to their groups because their damage is superior to tanks/casters, then we have an issue. Even with two high RR, very well temped assassins, I doubt I could get in a good visible group.
For the most part, a properly played tank/light tank should beat a relatively even RR stealther 1v1 unless things just happen to go the stealther's way. If you're dying to stealthers that are not swapping weapons, not applying multiples types of poisons, and not using any general toys or tactics, then the issue is with you. If an assassin plays properly, then yes, they should have a chance to win the fight.
From my experience on my assassins, there isn't a lot I won't attack solo, but that doesn't mean I'm going to win. I've lost a ton of 1v1s to tanks in my career, and I've won a lot too. After they boosted shield, I didn't even bother to attack most shield tanks - there were fights where I literally logged 20-30 swings in a row where my mainhand didn't land. I actually had a fight were 58 out of 60 mainhand swings didn't land. With shield's current state, it's still better than it was before they initially removed the DW bonus.
For my Savage, I pray that a solo assassin attacks me. Sure, I've lost a few fights, but that doesn't happen terribly often. If I pop my rr5 and Warguard, I can easily kill 3+ mediocre assassins and he's a very group friendly character.
I can agree that adjustments need to be made, especially to Nightshades - their nuke should either lose some damage or range. Nightshade damage was extremely useful before they boosted the damage - now it's just stupid, it's not even fun to play my Shade anymore with all the idiots playing the class now spam nuking everything

DD poison is stupid too
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Granas Lynokse - Lone Enforcer Shadowblade
Kienon Lynokse - Lone Enforcer Nightshade
rr6 Inf, rr6 Savage, rr8 Eld, etc.
CV: (Mid) Granfizzle, Granasz, Granan
(Alb) Gransil, Granfer (Hib) Granworth