Topple is just a variation on knocking prone. Sap and vex are disadvantage/advantage which is rolled right along with the regular roll. These are all very quick things.
No it isn't. It is twice as much (and in addition there is no size limit)
If I have a 20th level fighter in 5E I can either attack with a weapon 4 times or I can try to knock an enemy prone 4 times or mix and match between the two but I only get 4 "things" out of my attack action. If I try to knock an enemy prone I don't get to do a weapon attack ... In 5.5E I can do both every time I hit (and if I am a Champion reroll if I miss) and once I knock him prone me and all my allies are rolling twice for every single attack against him due to advantage or disadvantage.
But these are all interesting things that, for me (and my group), add fun and value to the game. So it's not a lag or even a slow down, though I certainly haven't seen any doubling. Point is, yes martials have a few more options, sure - I actually see that as a good thing.
I agree it adds fun and value for many players, but it is inconceivable that a PC can do more things, take more actions, more movement, make more attacks and roll more dice and not take more time.
It may not be a "drag" for you or your group and maybe you have not noticed, but it is has to take longer. You are doing far more things every turn in combat.
It's still high level casting with decision, placement and, often, multiple saving throws. And if you have prepared casters, you also have prepared martials.
Sure, but it is not nearly as many rolls over the course of a combat. There may be a ton of rolls when a caster casts Fireball or Cone of Cold or Hypnotic Pattern but those are one time and usually even when they use one of those spells it is not much more than the fighter is going to make or cause others to make on one attack action and they are not doing as much with it. Spells like Yolanda's Presence or Spirit Guardians can cause rolls for multiple enemies turn after turn, but most spells don't.
I cast Fireball and those 5 guys save and then there is one big damage roll and they either take full or half. It is not I attack this guy, roll damage against him, make him roll to go prone, then I use second wind roll to regain hit points, and move over here and attack this other guy and then roll a different damage number against him and make him roll to go prone, then since he is already prone I Sap him and roll damage a third time and then finally I try to grapple him to hold him down so he can't get up. That is more or less a typical Fighter turn at 20th level and it is happening over and over again except when they action surge and then it is even more they are doing.