The unusual rhyme scheme in Friar Laurence's soliloquy found in Act 2, Scene 3 is actually very similar to a satirical poem, and while it may not make him look exactly foolish, it certainly does point out that his actions are out of character.
Short satirical poems are written with quatrains, A, A, B, B, but longer satirical poems can continue the scheme and make up variations ad infinitum. In this soliloquy the rhyme scheme is A, A, B, B, C, C, D, D, E, E...all the way up to O, O. The rhyme scheme serves two purposes. For starters, it points out the irony of a Catholic friar out gathering herbs at dawn for magic potions. Secondly, since there is a great deal of irony in Friar Laurence's characterization, the rhyme scheme in the soliloquy also serves as a satirical attack on the traditions and behaviors of the Catholic Church.
The rhyme scheme is actually very reminiscent of a chant. Friar Laurence is outside gathering "baleful weeds and precious-juiced flowers" for the purpose of making both "poison" and "medicine" (II.iii.8, 23). While doing his gathering, he is chanting about nature. He opens his soliloquy by describing morning breaking, as we see in his opening lines,
The grey-ey'd morn smiles on the frowning night,
Check'ring the Eastern clouds with streaks of light,
And flecked with darkness like a drunkard reels
From forth day's path and Titan's fiery wheels. (II.iii.1-4)
While the rhyme scheme and Friar Laurence's chanting do not necessarily make Friar Laurence look stupid, it certainly points out a great deal of irony. Catholic friars do not gather herbs for both poisons and medicines, nor do they chant at dawn. The irony serves to portray this soliloquy as a satirical poem that pokes fun of Church activity and traditions. For example, out of respect for the ways of the Church, Friar Laurence is very bent on trying to end the violence of the feud. He is so bent on it that he agrees to marry Romeo to Juliet, thinking it will end the feud, even though he does not believe that they are ready for marriage. Hence, Friar Laurence represents hypocrisies of the Church in using the holy sacrament of marriage to end the sin of violence, which only creates more violence in return.
Hence, while Shakespeare is not necessarily trying to make Friar Laurence look foolish, he is portraying the irony of his character with the intent of satirizing the Church.