Do you mean pointswise, or "thats a cheap tactic" wise?
EIther way, I'd say the answer is no. For the points you end up paying for a 50 man conscript blob and a Lord Commissar, you could get almost as many guardsmen with a regular platoon and a normal commissar. Not to mention they can take special,heavy, and power weapons, as well as having a higher
BS and
WS, and a much higher
LD, all for 1 measly point extra. For example, 295pts either gets you...
1. a 50 man conscript blob, 1 Lord Commissar with Camo Cloak,
PW, and melta bombs OR
2. A 30 man blob of guardsmen (with a barebones 30pt
pCS for
FRFSRF) that has 3 meltas, 3
PW sarges, 1
PW commissar that can't get singled out, and the benefit of orders, the ability to kill something with shooting, and still has stubborn to keep from running away. And if I drop the
PCS from the equation (after all you still have to buy it to get conscripts) I could easily throw 3 autocannons in that blob as well.
Although those extra 20 conscripts may sound more helpful, think about it from this angle. They shoot like an ork, hit like a grot, and die like guardsmen. None of those are traits you want in an objective holder

And since you have to take at least 2 infantry squads anyways, it usually means that conscripts aren't really worth it, which is sad because I love the idea of them.
If you're asking tactics wise, no, it wouldn't be considered cheap either I think. Unless you're playing tau or something, even the most average of melee units could pull that blob off an objective if they wanted to, and with 2
WS on the conscripts and no power weapons besides a guy that can get singled out, they can't really kill anything in return. Not to mention the moment the Lord Commissar dies they'll run in a hurry... Heck, even a scout sentinel could pull them off and then proceed to tarpit them the whole game (if it kills the Lord Commissar of course)
Like I said, I hate having to say that. I would use conscripts all the time if I could think of a good use for them...