I don't think that stopping the rotation is a good thing to do. That's something newer players may fall into, but at least they have the correct mindset in trying to pull proper bursts. With experience I do feel that you actually find ways to adjust constantly to what is ready and what isn't. One of the big hurdles in learning MCH, at least for me, was to get out of the mindset that I must do THIS burst specifically without variation. It makes your job way too rigid and unable to adjust to what's happening. If your Drill or Anchor aren't primed for the end of a WF burst because you used them before to secure a kill without the burst (Drill because it deletes people guarding at low health, or even at higher health if your team is ready to pounce after, and Anchor because it's like Nocturne or Raiju, it's a stun so it enables bursting down people or chasing stragglers), then you can try and end the burst on Scattergun (which makes for a bigger potency WF in counterpart btw). You can also end the burst on a normal chainsaw, it's not dirty.

The burst can definitely kill people and it happens regularly, but it's not primarily made to secure kills, unlike using A.Drill and Anchor out of the burst. Its main function is to nuke defensive resources out of players and apply strong alpha damage pressure or just to burst players down with your team (if possible if they are also CCed by your team). It's way too cumbersome to set up and use in order to secure a kill, the target will have fled or healed or the opportunity gone way before you even finish setting up WF otherwise... In any case, you don't use the burst in the same cases that you'd use a lone Drill, Anchor, or Spite.

All in all I've never felt that my tools were not properly aligned for ages now. At best the thing that makes me wince is when I have to end a WF burst on Bio because even Scattergun is off, but that's rare, and tbh, it's still good damage.

The big difficulty in playing the job well imo is to be able to adust your toolkit to what OPPORTUNITIES you face at any given time. The kit is extremely flexible and is probably the job that offers the most combinations of things you can do, but it also comes at the cost of constraints in rotation and setups, which brings a certain amount of skillplay into it.

On Spite in FLs, I do agree it's extremely underwhelming, not only due to DR, but also because in CC it deletes 1/5th of the enemy team, while in FL it deletes 1/24th or 1/48th depending how you see it... if it deletes them since melees are too tough anyway, and you need BH4-5 to make it shine. But that's the harsh reality of LBs in FLs. It's not the only LB that's very mediocre here (have you heard of BRD's LB, the worse LB in existence in both worlds?). SCH LB in FLs is pretty laughable, WAR as well. Honestly they'd probably need to decorrelate FLs from CC on pvp and tune every pvp action a little differently with their own potencies, twists, etc. Adding some DR bypasses as you say on MCH, maybe, whatever does the job.