Depends on what you understand by decent amounts. My current Vit Conjurer has 2.739 OA and a Crit Chance of 20.2% against Valdaran and 19.4% against Mad Queen. Unfortunately I cannot facetank her, so she takes forever to beat, using hit and run.
Yeah, with 1900 OA, your crit chance against most bosses will be zero in Ultimate, and your chance to hit will probably be around 85-90%. I have a tank Commando I’ve been working on and while he can facetank pretty much everything, it takes forever to kill bosses with only 1900ish OA.
Are you using ACBs poison build? His build can use a lot of work. I have about 800 more OA over him even after a nerf to some of my gear. You can definitely get a lot more OA and it is a huge dps boost. I have a much more defensive devotion setup as well as gear, but kill much much faster
My Elementalist Mortar/Storm Totem build can easily farm the Mad Queen. With Flashbang and buffs I have over 2600 OA but mainly having 3 Mortars/3 Storm Totems and the 6 Thermite Mines kinda makes her pointless.
A little update. So, after much speed running and a few lucky drops along the way I was able to reach the mad queen and beat her on ultimate! I changed my build around a bit. Maxing BoD and switching some gear around. Now I have 2.3k OA and while the crit rate wasnt spectacular, it got the job done. Mind you im only at lvl 76 and my WitchHunter is far from full potential. I only have 4 pieces of my endgame set so i should be looking at about 2.5-2.7 when its all said and done. That i feel, will be a comfortable amount. No claw yet though :X