I'd check statistics first before worrying about index fragmentation.

SELECT SCHEMA_NAME(o.schema_id) AS SchemaName, o.name AS TableName, i.name AS IndexName,
    s.name AS StatsName, STATS_DATE(s.object_id, s.stats_id) AS StatsDate,
    si.rowmodctr AS RecordsModified, si.rowcnt AS TotalRecords, si.rowmodctr*100.0/si.rowcnt AS pct
  FROM sys.objects o
    INNER JOIN sys.stats s ON o.object_id = s.object_id
    LEFT OUTER JOIN sys.indexes i ON o.object_id = i.object_id
    LEFT OUTER JOIN sys.sysindexes si ON i.object_id = si.id AND i.index_id = si.indid
  WHERE o.type = 'U'
    AND o.name = 'xmlchanges'