Na, some run without them, but I think that really depends on the springs. With the RE springs I am running now I woulodnt like to run without the rear.
Was on an offcamber section of track the other day and felt like I wanted to climb out the window to make sure it didnt tip over... Without the rear swaybar I think I could have been in trouble.
Only problem with longer rear links is they may foul with the wheel, so you flip them to the inside - but then I found they fouled on the chassis... This was with the RE longer rear links. I took them off and replaced them with some PP adjustable ones, though they were too long too (rated at 2 to 5in) so I ended up trimming 40mm off them. The tops use a much thinner design so I no longer have issues with them fouling on the tyres.
This was the RE's flipped to the inside to clear the wheels:
This is the PP ones after shortening by 40mm: