I took a closer look at the query and you might be able to redesign it. Here is what I mean:

The LIMIT 0,50 portion of the query seems to be made busy in the query last.

You can improve the layout of the query by doing the following:

Step 1) Create an inline query to gather only keys. In this case, the id for blogposts.

Step 2) Impose any WHERE, ORDER BY and GROUP BY clauses on the inline query bringing keys.

Step 3) Impost the LIMIT clause as the last step of making the inline query.

Step 4) Join the inline query with the blogpost table in the event you need additional columns from blogpost as a blostpost temptable

Step 5) Join this new blogpost temptable with the articles table.

Steps 1-3 is meant to create a temptable with exactly 50 rows and include the blogpost id. Then, perform all JOINs dead last.

With these steps applied to your original query, you should have this:

SELECT /* [things omitted] */ articles.blogpost_id, articles.id AS articleid
FROM
(
  SELECT B.*
  FROM
  (
    SELECT id FROM blogposts
    WHERE date_published <= NOW()
    AND deleted = 0 AND visible = 1
    AND title LIKE '%{de}%'
    ORDER BY date_created DESC
    LIMIT 0,50
  ) A
  INNER JOIN blogposts B USING (id)
) blogposts
INNER JOIN articles
ON blogposts.id = articles.blogpost_id;

Since you edited the question and stated that you will remove LIKE, now your query should look more like this:

SELECT /* [things omitted] */ articles.blogpost_id, articles.id AS articleid
FROM
(
  SELECT B.*
  FROM
  (
    SELECT id FROM blogposts
    WHERE date_published <= NOW()
    AND deleted = 0 AND visible = 1
    ORDER BY date_created DESC
    LIMIT 0,50
  ) A
  INNER JOIN blogposts B USING (id)
) blogposts
INNER JOIN articles
ON blogposts.id = articles.blogpost_id;

In the phrase [things omitted], if you do not need anything from blogposts other than the keys, then your query should look like this:

SELECT /* [things omitted] */ articles.blogpost_id, articles.id AS articleid
FROM
(
  SELECT id FROM blogposts
  WHERE date_published <= NOW()
  AND deleted = 0 AND visible = 1
  ORDER BY date_created DESC
  LIMIT 0,50
) blogposts
INNER JOIN articles
ON blogposts.id = articles.blogpost_id;

CAVEAT

Make sure you build an index that involves the columns deleted, visible, and date_created as follows:

ALTER TABLE blogposts ADD INDEX deleted_visible_date_created (deleted,visible,date_created);

Give it a Try !!!

I have a few suggestions that may help

SUGGESTION #1 : Use index with different column order

ALTER TABLE sales_reps ADD UNIQUE INDEX
(state,account_id,name,platform,client_group,from_date);

Note that state and account_id are reversed. That way, there is no need to traverse all rows for a given account_id that would separate enabled from disabled. Only enabled entries for account_id are read.

SUGGESTION #2 : Refactor the Query

Instead of

SELECT * 
FROM `sales_reps` 
WHERE `sales_reps`.`account_id` = 1 
AND state = 'enabled' 
AND (clients >= 1 OR revenue >= 100) 
ORDER BY name,platform,client_group,from_date

Try this experiment

First run this query

SELECT enabled,accountid,name,platform,client_group,from_date
FROM sales_rep WHERE account_id=1 AND state='enabled'
ORDER BY enabled,accountid,name,platform,client_group,from_date

then run this query

SELECT * FROM sales_rep WHERE account_id=1 AND state='enabled'
AND clients >= 1 OR revenue >= 100

If the performance of those two queries are fast, then JOIN them as subqueries and see

SELECT B.* FROM
(
    SELECT enabled,accountid,name,platform,client_group,from_date
    FROM sales_rep WHERE account_id=1 AND state='enabled'
    ORDER BY enabled,accountid,name,platform,client_group,from_date
) A LEFT JOIN
(
    SELECT * FROM sales_rep WHERE account_id=1 AND state='enabled'
    AND clients >= 1 OR revenue >= 100
) B USING (enabled,accountid,name,platform,client_group,from_date)
WHERE B.enabled IS NOT NULL;

Give it a Try !!!