Let's try and figure out what the height and weight of a guardian is. Besides NPC's guardians all have the same height and weight it seems. So let pool all available info and see what we can come up with.
The obvious so far
Titans seem to be the heaviest
Warlocks are medium builds.
Hunters seem to have the lightest builds.
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Titans are about 6' to 7', and weigh 500-1000 pounds