By default, the Best in Slot feature does not consider warforged items. It only does so when you specifically change an item to a different ilvl in the “Customize Gear” window.
This is confusing, because in a lot of cases (usually rings and trinkets) a 300+15 item might be better than another 315 baseline item.
Let’s take this example:
We’re looking for the BiS trinkets for an affliction warlock, set at ilvl 370. When I click the button, Mr. Robot will find the best options but only considers the baseline ilvls for each item. Meaning it will completely let out trinkets like “Pearl Divers Compass” and “Balefire Branch” because those are baseline 340 trinkets. Manually customizing those trinkets to ilvl 370 will however show the correct rating of those items.
The initial BiS suggestion is not correct if it only considers baseline ilvls. Yes, titanforing +30 or higher is extremely rare, but in some cases the value of those trinkets outshines anything else.
I’d like to see this worked out a little better. Maybe add an option to include titanforing into the BiS considerations.
EDIT: My example is a bit off. Selecting the Mythic+ level helps in some way for items that drop in mythic dungeons, but that’s not a solution. If we took the same example and said “I want the BiS list for iLvL 390” then the Mythic+ option would not help, since it will consider all dungeon loot at baseline 370 then.
I’d say the main question here is: What would you really gain from having that info?
As you said yourself, the chance to get such a high warforge/titanforge is extremely rare. So rare in fact that you absolutely can not plan your personal BiS around it since you will most likely never even see it and are even less likely to get one yourself on the exact item you’d need to.
Including titanforging in BiS lists would cause those lists to become pretty useless as you’d have to check for every single item and depending on the available stats you might get something like “use item X from World Quests with a titanforging of +75 item level”. This would be practically impossible to obtain and depending on luck not even one single character worldwide might own that item.
If you get such an item, then AMR will include it in your BiS calculations but as long as you don’t have it, there really is no need to. AMR calculates a BiS list of items that are readily obtainable by just playing the content you want, not by doing so and (if you look at the chance depending on the extent of necessary titanforging probably literally) getting the main prize in the lottery far over a dozen times.
Of course, if you take the phrase “Best in Slot” literally, this would be the correct approach - but it would serve no purpose as you couldn’t really do anything with it. That’s one of the most important places where Blizzard’s philosophy changed significantly over time and we as players need to adapt to that. An absolute “Best in Slot” is (by design!) no longer attainable.
I’d say a possible optimization there could be to have an easier way to find out at which item level an item would be comparable to your current gear, especially for trinkets and/or rings - but that would probably use an exorbitant amount of calculations and showing that data in a well laid out way might also be difficult.
The main reason we don’t consider warforged/titanforged items for BiS is because you have no control over when you get them. If you get a good roll on an item, you have it - and then you can check to see if it is an upgrade for your set. You don’t really, as a player, particularly “try” to get warforged versions of specific items, since that would take forever. You just happen to get them sometimes.