Translation: Among them [i.e. Erasmus's friends], my dear More, you certainly [ vel ] have always stood in the first rank; in your absence I used to enjoy thinking of you, just as much as I had enjoyed your intimate friendship when in your presence; I think I'd perish [of delight] if anything more enjoyable touched me.Inter hos tu, mi More, uel in primis occurrebas; cuius equidem absentis absens memoria non aliter frui solebam quam presentis presens consuetudine consueueram; qua dispeream si quid unquam in uita contigit mellitius.
I don't understand the sense of "absentis absens . . . praesentis praesens". I assume absentis . . . praesentis agree with cuius, and absens . . . praesens agree with the first-person subject of consueueram.
I have made a free translation because I'm struggling to get the literal word-for-word meaning. I'm unhappy with my understanding of the sequence of tense.