Yes, if you're looking for a numerical 1, 2, 3, ... 25, 26, 27 ordering of amendments, the current thematic arrangement might indeed seem confusing.  That confusion should however, subside after a few moments as you consider why each particular amendment is in the group that it's in. 

 Regarding amendments 11–27, 
 *Governmental authority: 11 (authority of federal courts to hear cases against states), 16 (authority of Congress to impose/collect direct taxes), 18 (authority of Congress to regulate alcohol)& 21 (authority of states to regulate alcohol) 
 *Safeguards of civil rights: 13 (abolition of slavery), 14 (citizens' immunities, privilege and protections) , 15 (voting rights expansion), 19 (voting rights expansion), 23 (voting rights expansion), 24 (breaking down voter suppression)  & 26 (voting rights expansion) 
 *Government processes and procedures 12 (electoral college process reform), 17 (procedure for electing US senators changed), 20 (start date for Presidential, Vice Presidential and Congressional terms changed), 22 (rule established for how many terms/years a person can serve as President), 25 (procedures & process regarding presidential succession modified) & 27 (procedural change regarding Congressional pay increases) 
 I suppose XIII and XIV could go under "governmental authority", and the group containing XV, XIX, XXIII, XXIV & XXVI could be renamed "voting rights".