@Rook - your going to be so glad you asked… I’m in a detailed response kind of mode today so you may have to dig a little bit for your answer LOL! 
I THOUGHT GUINEVERE WAS RANKED #1? WRONG!
Gravemaker is without ANY doubt and by FAR #1. ZERO doubts. Data doesn't lie. You can basically place him in ANY POSITION and get results - FLANK is certainly his STAR/strong position. He is also by far the most duplicated hero on teams, and it's becoming a trend.
(Side note: I would be highly interested to know how many Gravemakers were distributed during his 30 day HOTM offering as based on data it seems to be much higher than several/many of the other HOTM. Logically if he was more desired, there were more summons, then end of story. SGG may not put a cap on distribution for HOTM's during their availability. More of a curious thing for me).
Guin on the other hand battles with Alasie, Sartana and sometimes Zeline for the 2, 3, 4 and 5 spots of the Top-5. She usually brings up the rear - being she was/is built uniquely for the TANK/CENTER role - she is used primarily in 1 of 5 positions whereas Alasie for example can be used on 2 (in general for best results - REAR Left or Right).
I did write an article about GUIN - THE MOTHER OF ALL MOTHERS in which I discuss her:
TIME OF AVAILABILITY FACTOR (TofA)
and propose a hypothetical - which is just that - showing how she could be #1 in terms of USE on a team (being 100% vs Gravemakers 82-85%). That was then, and it was a hypothetical proposal (more of a WHAT IF? scenario). Gravemaker is and has been #1 for Months. She could potentially be used 100% of the time however… that is impossible due to TofA. If you’re interested here is the link to the article - I would rewrite it today based on data collection as well the research I have done since… still an decent read I think:GUIN: THE MOTHER OF ALL MOTHERS (Click to Read - Note: this is a dated article)
WHERE DOES THE DATA COME FROM? I'LL TELL YOU...
The data you came across is a small subset of summarized data from the Data Warehouse used by the ‘Hero Utility’. Each week data is collected from multiple sources as well many calculations are run to generate NEW data and Summarized results, thus producing that week’s data for the Hero Utility.
If you visit TitanMafia.com just go to the section ‘THE WEEK in REVIEW’ or jump there via:
WEEKLY REVIEW (Click for Access)
If you want direct access to the Summary Tables of data such as which LEGENDARY heroes were not used (great list to watch over a couple weeks to identify whom to set aside for a possible future SGG ‘balancing’ and not waste time/resources for a 4th Ascension at this time) and what EPIC heroes were used (identifies some likely EPICS who have life after your EPIC phase). You can go the [LATEST REPORT] through the ‘Hero Utility’ itself or jump to the entire archive available to EVERYONE through:
Each of the reports provides the historical links to the priors so you can delve down to the very first data collection from 7/29/2018 if you want to. It clearly reveals the progression of collection, the adjustments along the way, and the future of the utility etc…
Every week a pool of 500 heroes are collected from the LEADERBOARD (Top-100 players) in detail and added to the Data Store. It is a proven method of collection. In particular the current data - it cannot be disputed, period. If it is, you can slapped with the Historical data that backs it up!
Historical RANKS (-- CUMULATIVE --) data - some will argue their accuracy based on Time of Availability (TofA) of Heroes. I don’t disagree - still EXCELLENT information to have. And it is FACTUAL for the Hero you are reviewing, PERIOD. I have written about TofA and though it is speculative - a FACTOR may be developed specifically for the CUMULATIVE statistics - not necessary - but a future consideration.
GPA’s are provided by the Hero Utility. Pretty straight forward using the standard USA based 4.0 Grading system (simple calculations). GPAb (is the blending of the Offensive and Defensive Data - being this is the Blend that is used in ALL battle scenarios outside of TITANS in regards to GRADES).
RANK and GRADING and adjustments to those are also included - BOTH should be and are huge considerations for selecting your next Hero to ASCEND to FULL POWER! Or with Adjustments to consider start using (this is a rarity - but happens).
I’m sure much of what I said above is better said through TitanMafia.com or the Hero Utility links.
Anyone who puts in a fair amount of time to playing this game on a daily basis, who is here for the long haul - as this is a LONG TERM commitment game… Anyone who wants to be INFORMED/Up-To-Date, who has ANY interest in making informed ASCENCION decisions (4th that is) and VALUE placing their HEROES for best results - would be a FOOL by not allocating a few minutes a week to get the LOW-DOWN.
The Weekly review and data collection update is Usually available SUNDAY MORNINGS - grab a cup of Jamoke - and get informed!
LOL - thanks for the lead in. Hope it answers your question if not I can readdress in another thread.
Best additional links for consideration I would say are the following:
Grading Scale
About and Select Game FAQS
RaZoR
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