WRT DSTs/BRs and the BCs:

Everything that's a "thing" in EVE, from planets to ships to trit, sits in a three level heirarchy of type (Omen), group (Cruiser), category (Ship).

The type encapsulates all the data specific to that actual thing, so every time we make a new "thing", we make a new type. At the other end of the spectrum, it's pretty rare that we have entirely new categories of thing, so the list of categories is fairly constant and caterogization serves mainly to break types up along pretty fundamental lines (a celestial is not the same thing as a module).

In between these two levels sits the groups, which end up doing a fair amount of heavy lifting as doing things "by group" gives us the ability to affect related sets of types at a nice level of granularity, ie without either special-casing per-type (which makes adding other, similar types a pain) or going up to the category level (which affects very large numbers of types in a fairly indiscriminate manner.

So, BRs and DSTs. They've always been referred to as those two separate things in their descriptions, and they serve separate roles, but previously they were all in the same group as, despite their stats being wildly different, they were sufficiently "functionally the same" to not need group-level separation.

The thing that changed in this patch is that we've made an effort to get rid of "CPU hacks" to restrict modules - the "99% reduction to CPU use of blah" that we used to kep, for example, covops cloaks or warfare links restricted to certain ships. It's a thoroughly ingenious solution to the problem that leverages our content tools to enforce restrictions without requiring new code, and thus "back in the day" was an eminently practical way to solve the problem of "not every ship should be able to warp cloaked". However, it's also somewhat hacky and unintuitive and has generally poor UX, which makes us sad.

Since this was originally done, we've gained a new tool, called "can fit to group", which allows us to tell a module which specific ship groups it can be fitted to. This is nicer and cleaner and less hacky and we generally prefer it, so in Retribution 1.1 we've made the final push to eliminate the old "99%" solution and use "can fit to group" instead.

Those of you following along at home will see where this leads us to, though: in the case of the covops cloak, for example, we want to fit to the BRs but not the DSTs, but to do that in the new system they need to be in separate groups, so they've been split thusly. The same thing happened with warfare links and battlecruisers: if they're functionally different in terms of what modules they can fit, they have to be in separate groups. In the case of T2 industrials, the distinction has always existed on paper, but now it exists in the type hierarchy as well

[edit] Oh yeah, one other thing... 10 points for the first person to spot the place where this paradigm still doesn't work nicely, and 50 points for the first person to guess how we're solving that right now