I don't really agree with this, at least IMO. There are a lot of poor 2nd level channel divinity options, but the Knowledge, Light, Tempest and Trickery domains all have very potent channel divinity options, all of which I would put ahead of Preserve life.
Let's see how well those do when used at 6th level.
Radiance of the Dawn: 2d10+6 points of radiant damage to all hostiles within 30 ft, plus dispelling magical darkness. 17 points of selective AOE is OK, with a situational additional benefit.
Knowledge of the Ages: +3 to a skill you're not proficient in for 10 minutes. It can be clutch, but it's highly situational. I'll grant that Read Thoughts is great, but my comparison was with the basic 2nd-level Channels.
Destructive Wrath: It will increase a shatter upcast to 3rd level from 4d8 (average 18) to 32 points - a bonus of 14 points in a small AOE. If you're in the right circumstances (outdoors in a storm) it might instead increase a single bolt from call lightning from 4d10 (average 22) to 40, a bonus of 18 points, but in most cases it would be 3d10 (average 16) to 30, a bonus of 14 points. Both spells have fairly small AOEs (10 ft radius for shatter, 5 ft radius for call lightning). Now, if you somehow have the ability to cast lightning bolt instead, this becomes more impressive (from average 28 to 48 damage, +20, with a huge AOE), but that requires something outside of the class (multiclassing or an item).
Invoke Duplicity... yeah, I can see your point there. It does eat your concentration unlike most other uses of Channel Divinity, but on the other hand it does allow you to project your spells up to 120 ft away, or to get advantage on melee attack rolls. That's fairly nifty, albeit situational.
And finally, Preserve Life. It heals 30 points of damage, spread out among any number of recipients within 30 ft. It can bring back a fighter from death's door to half their hit points (well, almost), or bring several PCs that just got hit with an AOE back into reasonable numbers of hps. If it was just 30 hp healing, it would be merely OK, but it's the versatility that lets you either focus all the healing on a single target or top off multiple allies that I like about the ability.
I'll add that Radiance of the Dawn, Knowledge of the Ages, and Destructive Wrath all make the cleric better at something clerics are normally bad at - either giving a skill proficiency the cleric normally doesn't have, or doing AOE damage. But Preserve Life makes the cleric better within their main area of expertise, namely healing.