Хотя судя по текущим запросам к Вашей БД могу сказать что больше всего нагрузку создают подобный запросы:
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 # User@Host: p56267_kdoc[p56267_kdoc] @ [91.218.229.10]
 # Thread_id: 31676017 Schema: p56267_kdoc Last_errno: 0 Killed: 0
 # Query_time: 0.383857 Lock_time: 0.000329 Rows_sent: 5 Rows_examined: 5789 Rows_affected: 0 Rows_read: 5
 # Bytes_sent: 35152 Tmp_tables: 5 Tmp_disk_tables: 1 Tmp_table_sizes: 89749144
 use p56267_kdoc;
 SET timestamp=1349135464;
 SELECT a.fulltext, a.id, a.title, a.alias, a.title_alias, a.introtext, a.state, a.catid, a.created, a.created_by, a.created_by_alias, a.modified, a.modified_by,a.publish_up, a.publish_down, a.attribs, a.metadata, a.metakey, a.metadesc, a.access, a.hits, a.featured, a.ordering, c.alias AS category_alias, LENGTH(a.fulltext) AS readmore,a.fulltext, a.id, a.title, a.alias, a.title_alias, a.introtext, a.state, a.catid, a.created, a.created_by, a.created_by_alias, a.modified, a.modified_by,a.publish_up, a.publish_down, a.attribs, a.metadata, a.metakey, a.metadesc, a.access, a.hits, a.featured, a.ordering, c.alias AS category_alias, LENGTH(a.fulltext) AS readmore,c.title AS category_title, c.path AS category_route, c.access AS category_access, c.alias AS category_alias,CASE WHEN a.created_by_alias > ' ' THEN a.created_by_alias ELSE ua.name END AS author,ua.email AS author_email,contact.id as contactid,parent.title as parent_title, parent.id as parent_id, parent.path as parent_rou!
  te, parent.alias as parent_alias,ROUND(v.rating_sum / v.rating_count, 0) AS rating, v.rating_count as rating_count,c.published, CASE WHEN badcats.id is null THEN c.published ELSE 0 END AS parents_published
 FROM doc_content AS a
 LEFT JOIN doc_content_frontpage AS fp ON fp.content_id = a.id
 LEFT JOIN doc_categories AS c ON c.id = a.catid
 LEFT JOIN doc_users AS ua ON ua.id = a.created_by
 LEFT JOIN doc_users AS uam ON uam.id = a.modified_by
 LEFT JOIN (
 SELECT contact.user_id, MAX(contact.id) AS id, contact.language
 FROM doc_contact_details AS contact
 WHERE contact.published = 1
 GROUP BY contact.user_id, contact.language) AS contact ON contact.user_id = a.created_by
 LEFT JOIN doc_categories as parent ON parent.id = c.parent_id
 LEFT JOIN doc_content_rating AS v ON a.id = v.content_id
 LEFT OUTER JOIN (SELECT cat.id as id FROM doc_categories AS cat JOIN doc_categories AS parent ON cat.lft BETWEEN parent.lft AND parent.rgt WHERE parent.extension = 'com_content' AND parent.published != 1 GROUP BY cat.id ) AS badcats ON badcats.id = c.id
 WHERE CASE WHEN badcats.id is null THEN a.state ELSE 0 END = 1 AND (a.publish_up = '0000-00-00 00:00:00' OR a.publish_up <= '2012-10-01 23:51:03') AND (a.publish_down = '0000-00-00 00:00:00' OR a.publish_down >= '2012-10-01 23:51:03')
 GROUP BY a.id, a.title, a.alias, a.title_alias, a.introtext, a.checked_out, a.checked_out_time, a.catid, a.created, a.created_by, a.created_by_alias, a.created, a.modified, a.modified_by, uam.name, a.publish_up, a.attribs, a.metadata, a.metakey, a.metadesc, a.access, a.hits, a.xreference, a.featured, a.fulltext, a.state, a.publish_down, badcats.id, c.title, c.path, c.access, c.alias, uam.id, ua.name, ua.email, contact.id, parent.title, parent.id, parent.path, parent.alias, v.rating_sum, v.rating_count, c.published, c.lft, a.ordering, parent.lft, fp.ordering, c.id, a.images, a.urls
 ORDER BY a.hits DESC LIMIT 0, 5;
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 Таких запросов много.