Raw Power... and Cantrips

Signature Spell

I'm working on a revised magic system for use with my Templar class. I want it to be roughly equal in power to the Warlock, but I don't want the schtick of Eldritch Blast being an effective class requirement. In developing my own 'Cantrips', I realised one thing: some of the cantrips are actually really powerful.
I play an Eldritch Knight in my Wednesday night game. While I have a crossbow, I hardly ever use it, because Fire Bolt is 2d10 (my character is 9th level) fire damage over 120 feet and I can use it as an AOO (War Caster), and I can do a bonus weapon attack right after using it as my action, so potentially 4d10 + weapon damage in a single round of combat. Right there and then is my go to ranged weapon.

For the Warlock, Eldritch Blast is the equivalent, mostly because it ties in with so many of the Eldritch Invocations available to the class. It is the signature at-will power for the class. I want my powers to be a little more flexible, but I get the impression that there is one, or maybe two, that will be go-to powers for the class, for example:

Fist of the Templar

Enchantment cantrip

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• Casting Time: 1 action
• Range: 120 feet
• Components: V, S
• Duration: 1 round

You call out to an enemy or wrongdoer to halt and bring your fist into your other palm. A loud sound rings out in an area of 120 feet (perhaps a thunderclap, a gavel pummelling, or a judgement bell tolling once).

You make a ranged spell attack against the target. On a hit, the target takes 1d6 psychic damage and its speed is reduced to 10 feet until the beginning of your next turn.

The cantrip’s damage increases by 1d6 when you reach 5th level (2d6), 11th level (3d6) and 17th level (4d6).

Being able to slow and harm a creature at the same time makes it useful. I'm considering actually upping the damage to a d8, but I'm not sure (suggestions welcome). Many of the powers available to my Templar cause psychic damage, as the focus is imposing the will of the Sorceror/Undying King. So, this features is one I think could become signature, but only if the focus of the campaign is combat centric.
Some of the other features simply come with the note "This feature functions identically to the <name> cantrip." That's easy enough. I know these features come with built in balance.
The only way to know how this will work out in the long term is to monitor. If players testing my Templar class default to these options every time, then perhaps the feature is too powerful. Either that, or I'm not putting together adventures/encounters that provide for use of the other features.
Next time, I'll go into some detail about the magic system. As the characters are at quite low levels, this hasn't been tested robustly yet, so this will be very much a basic introduction.