see edit. I mangled it somehow. what I was meaning was, if you have "two primaries", and your primaries do the same general thing, then you've got a lot of overlap
you still haven't explained why animation cancelling is even any good. a couple frames in a game that's so far online only is pretty meaningless.
burst combos can be and are effective. maybe there's no reason not to animation cancel. but none of this explains what makes bursts "top tier".
and now we will also have the problem of confirmation bias where anything that comes as a result of animation cancelling will be seen to be the result of animation cancelling and not whatever it actually was.
Alright, a lot to cover here, I'll try to break it down so that you understand where I'm coming from instead of just taking my word for it.
In terms of my calling it an additional primary, it definitely not about sustain, but about DPS. Burst bombs are essentially one of the highest DPS weapons in the game, and they are perfectly accurate with variable range depending on your gear. The other subs being a delayed explosion cannot function like a main weapon, not to mention their overall damage vs ink consumption is worse. Think of Burst Bombs as a really inefficient, high DPS weapon. So what does that effectively mean, well it means that you can couple high burst DPS with a weapon like the nozzlenose or splattershot that both have high sustain, that is what increases versatility, you now have two ways to approach an engagement, that isn't something you get with Splat and function bombs, at best you could hope to martyrdom with them. Second, burst bombs are behind only disruptor and point sensor in being an initiate, they have high range, AoE, and most importantly
extremely low end lag. Whereas shooting blind into enemy ink with most weapons leaves you vulnerable during your ending animation phase(especially rollers and blasters) burst bombs don't have that issue, not to mention with range ups it is by far the best blind spot check in the game, forcing people out from hiding or killing them if they don't move. It gives weapons an AoE indirect fire option when they wouldn't otherwise have one. That's a huge deal on something like the Nozzlenose.
Moving onto burst cancelling, I really don't get what is so hard to understand with this one, like all PvP games, having any kind of frame advantage is something you 100% want to have. BXR, RRX, BXB, YY, all of these techniques in Halo 2 could be the difference between getting a kill and dying, and they only saved you a couple frames. Roman Cancels and Counter Assaults in Guilty Gear/BlazBlue are so potent an animation cancel that they cost a full super. In other fighters characters live and die by their frame data. For me using theDolphinNose, a burst cancel kill is the maximum DPS I can achieve, and that is very often the difference between me dying and living when someone gets in my face. There is only
gain to be had through animation cancelling, and the Burst Bomb is the only Sub capable of it, that's why to me, it is the best one in the game.