In my opinion, bug that's been known by players for sometime, not sure if devs are aware or not; don't think we ever got confirmation. Videos were posted a patch or two ago on the PTS showing light/heavy attacks completely missing a close by target.

This has to do with the funnel health animation and the way it clips.

For a while some build guides suggested sticking with force pulse so that you could light attack in rotation.

Other build guides suggested medium attack weaving, which netted more long fight dps due to fewer resources used to sustain funnel over pulse, and mediums always worked over light not always working and the consistency and resources were preferable.

Most guides now suggest figuring out exactly the animation and then light weaving around it

I find the best way to do this is to think of it as light attack ➡️ funnel as one piece that flow together

You have to ever so slightly delay the light weaves for funnel health and the merciless resolve bow procs. Then for the rest of your skills, you can light weave them normally like you would on your magsorc. Yeah its kind of weird and annoying, but once you get more playtime down on your magblade, you'll get used to it and it will hopefully become second nature.

For reference, I usually need 1.10-1.15 seconds per light attack, which averages out at 53 light attacks per minute (in a full light attack rotation). This is slightly lower than I can manage on a magsorc weaving force pulse, and its down to funnel health and merciless resolve.

It's very annoying! It's so easy weaving with force pulse and other skills.
Not being able to do it properly with the NB's spammable skill makes me sad
The funnel animation clearly needs some minor tweaks

Funnel health is the hardest to weave spammable ability in the game due to the way its animation works. You just have to practice A LOT to get it down.

Medium weaving is an option, but if you are medium weaving, you are casting abilities slower than the global cooldown allows, so your DPS will be lower than someone who can perfectly light weave.

This is hard! And sometimes annoying, it's been like this since the last time they worked on AC.

In the evening I have these problems too. Even the cancelled LA with 'Suprise Attack' on my Stamblade don't stack properly then.