Here's a great resource for people who struggle with just getting into that "gotta go fast!" mindset:
Use it, or a willing friend or family member and a stopwatch, to practice sketching outside of making your comic. Some people like to do this digitally, others on paper. You'll quickly learn, probably after a few attempts, that to successfully draw something recognisable as full the pose within the time limit, you need to quickly prioritise just the most important lines, and that you need to just go for it, just sweep your pencil lightly across the page like woosh, and if you make a mistake, don't waste time erasing the line, draw another line and then reinforce the "correct" one with another, stronger stroke.
A lot of people don't like to experiment or change up their drawing pipeline while in the middle of a comic project, or at least on comic pages, because they don't want their pages to start looking inconsistent, or with worse quality than existing pages, so they stick to the recipe they already know. This is why I recommend doing drawing studies outside of comics, or even to take a break from making a regularly updating webcomic to spend on personal development.
I totally get that, now that you're able to get a consistently neat looking result when you draw things in your comfort zone, like say a person drawn from the front, the idea of going back to reinvent how you draw, knowing that these practice drawings from outside your comfort zone will probably look bad at first. You will probably draw a lot of sketches that you immediately scribble out or ball up and throw in the bin, or erase or close the canvas on without saving. practically every artist I know does this, and you don't need to show your sketches to anyone if you don't like them.
Over time and with practice, the habits you build up for efficient, confident sketching will start to speed up how you draw generally.
In a comics context, I find that having a tight deadline can help if you go in with the mindset of "whatever is finished by 6pm, that's what I'm uploading, and if anyone's got a problem with that, they're not being fair on somebody making them content every week!" My comic panels are not as polished as my standalone illustrations, and if anyone has a problem with that, well, that's their problem, 'cause I'm making them 6-12 or so panels of content a week on top of my job to a pretty decent standard. Sometimes it looks a little rough, but who cares!? It's a comic, most people only spend like 5 seconds looking at any given panel. So second piece of advice: Learn to let it go, and pick your battles. Not every panel can be a work of art.
Practical tip: Draw your comic at about 1.5x or 2x the size you'll print or publish it online at. It will hide so many small wobbles and imperfections, which means less fussing and faster page creation. 
Final silly, but weirdly effective tip: Put on some fast-paced music. If I need to blitz through an action scene, I put on my "GET HYPE!" playlists. They're full of like... videogame fight music, silly intense rock songs, or even trance. Lose yourself in the music, cut loose! Sometimes I even do a bit of shadow boxing or have a little workout before I draw to get me into that "go go go! Get the lines drawn! Stop fussing over tiny details!" mindset.
