1. Yes you have to go dex. God forbid a cleric go dex?
Exaggerated emphasis yours, not mine.
2. If you go dex medium armor is fine.
No, it really isn't... you are better off just going light armor at that point and pure dex focused since it is your primary stat with that awesome dagger. Dex, Wisdom, Con is a little MAD but not terrible.
3. At range: Use a crossbow. It stays equal or above sacred flame.
At very low level, yes that is true.
4. In melee use sacred flame (a dagger functions about the same early as sacred flame).
5. No idea why you would think starting fighter or rogue mattered. Clerics get most of their damage with spells. Bless, Spiritual Weapon, Spirit Guardians etc.
It seems as though your focus is on, how "less poor" they are than other 1st level characters. The game does go past 1st level though.
So let's see what the trickery cleric gets that's really awesome.
A. Blessing of the Trickster. One of my absolute favorite cleric domain tricks. For a solo scout mission you give the rogue advantage on stealth checks. For a party stealth mission you help that heavy armor wearing fighter so he doesn't immediately draw attention to the whole party any more. Amazing!
Not as good as Pass without a Trace. Not so Amazing! Their one spell is massively superior to this ability and doesn't require a specialized class ability. In fact, many classes get the spell.
B. The spell list is packed with goodies that clerics don't normally get. Some of them are amazing and some are fun and situationally strong.
Pass without trace (great spell especially when coupled with blessing of the trickster)
Polymorph
Disguise self
Mirror Image
Dimension door
I will give you that the trickery domain's channel divinitys are pretty bad. The capstone for the trickery domain is also pretty meh. So yea, if you are looking at level 17+ the subclass is lacking. Anything before that though seems fine.
Some of the spells are decent, admittedly... but they don't make up from the Subpar rest of the sub-class. It's a sub-class desperately in need of booming blade, sneak attack... something for the combat pillar. Yes you could play generic cleric style ignoring the trickery aspect, but it almost screams for multi-classing with its features.
Multiclassing rogue and fighter are so blatantly obvious it almost feels silly to point them out. Fighter for Second Wind, weapon proficiency, heavy armor (because Pass without a trace and guidance make it superior), getting a real bow, finesse weapons, Action Surge, the choice of Strength vs Dex, etc.
Rogue is for all those awesome dex skills and actual damage that would make this class exceptionally useful with its ability set.
I get that you like the Trickery domain... cool. It's still notably subpar compared to pretty much any of the other cleric domains.