The following calcs compare the damage output of Bait vs. MfD vs. Sentry against a single target.
Assume 50% CC. Assume 400% CD. Assume 2 aps. Assume 2500 Dex. Manticore user using bombardment rune.
DMG = ((1+CDxCC)x(APS)x(DEx/100+1))*Skill modifier.
Standard damage: The player would normally do (1+4*0.5)x2x(2500/100+1)*414 = 3x2x26x414 = 64584 times weapon dmg.
Sentry: 1 sentry would add (cannot crit): 2x(2500/100+1)*175 = 9100 times weapon damage
1 Sentry has hence increased damage output by (9100+64584)/64584 = 14.1%
Bait the trap: The player would do (1+4*0.6)x2x(2500/1100+1)*414 = 3.4x2x26x414 = 73195
Bait has increased damage output by (73195/64584) = 13.3%
Both of the above would outperform MfD which adds an additional 12% damage to one marked enemy.
Sentry: I have assumed one sentry noting that due to cooldown most fights you will not be have both up. Having both up gives you 28% more damage output. Please note that I am assuming a Xbow user and that a bow user who has stacked APS/DEX would weigh results more in sentry's favour. Sentries also continue to pump out damage even when you are moving around and not attacking. For a RF user, Guardian Turret would normally be the most appropriate.
Bait the trap: A key factor here is I have assumed single target. As Bait applies the benefit to you, if you are using an AOE attack like bombardment then the increased damage output also is AOE compared to Sentry/mfD which normally affects one mob. If you have a spare passive, Bait can even give you more damage with CtW.
MfD: This is the weakest one in my view for solo play. A lot of the runes are single target in nature and it loses out to sentry in single target damage output. Valley of Death has the highest damage output for AOE attacks but this is still worse than Bait.
Overall Winner: Sentry
Bait is best from a pure damage view point (if you are using a AOE attack). If you are not using an AOE attack then Sentry>Bait>MfD. On the face of it I will choose sentry as it delivers similar damage and continues to provide damage output even if you move around as opposed to just standing in a small area. Bait only provides damage with snare being largely irrelevant except for procing CtW. The Fuardian rune for sentry can provide both eHP and eDPS.